Starvation transforms signal encoding in C. elegans thermoresponsive neurons and suppresses heat avoidance via bidirectional glutamatergic and peptidergic signaling

Starvation transforms signal encoding in C. elegans thermoresponsive neurons and suppresses heat avoidance via bidirectional glutamatergic and peptidergic signaling | bioRxiv /* */ /* */ <!-- <!-- /*! * yepnope1.5.4 * (c) WTFPL, GPLv2 */ (function(a,b,c){function d(a){return"[object Function]"==o.call(a)}function e(a){return"string"==typeof a}function f(){}function g(a){return!a||"loaded"==a||"complete"==a||"uninitialized"==a}function h(){var a=p.shift();q=1,a?a.t?m(function(){("c"==a.t?B.injectCss:B.injectJs)(a.s,0,a.a,a.x,a.e,1)},0):(a(),h()):q=0}function i(a,c,d,e,f,i,j){function k(b){if(!o&&g(l.readyState)&&(u.r=o=1,!q&&h(),l.onload=l.onreadystatechange=null,b)){"img"!=a&&m(function(){t.removeChild(l)},50);for(var d in y[c])y[c].hasOwnProperty(d)&&y[c][d].onload()}}var j=j||B.errorTimeout,l=b.createElement(a),o=0,r=0,u={t:d,s:c,e:f,a:i,x:j};1===y[c]&&(r=1,y[c]=[]),"object"==a?l.data=c:(l.src=c,l.type=a),l.width=l.height="0",l.onerror=l.onload=l.onreadystatechange=function(){k.call(this,r)},p.splice(e,0,u),"img"!=a&&(r||2===y[c]?(t.insertBefore(l,s?null:n),m(k,j)):y[c].push(l))}function j(a,b,c,d,f){return q=0,b=b||"j",e(a)?i("c"==b?v:u,a,b,this.i++,c,d,f):(p.splice(this.i++,0,a),1==p.length&&h()),this}function k(){var a=B;return a.loader={load:j,i:0},a}var l=b.documentElement,m=a.setTimeout,n=b.getElementsByTagName("script")[0],o={}.toString,p=[],q=0,r="MozAppearance"in l.style,s=r&&!!b.createRange().compareNode,t=s?l:n.parentNode,l=a.opera&&"[object Opera]"==o.call(a.opera),l=!!b.attachEvent&&!l,u=r?"object":l?"script":"img",v=l?"script":u,w=Array.isArray||function(a){return"[object Array]"==o.call(a)},x=[],y={},z={timeout:function(a,b){return b.length&&(a.timeout=b[0]),a}},A,B;B=function(a){function b(a){var a=a.split("!"),b=x.length,c=a.pop(),d=a.length,c={url:c,origUrl:c,prefixes:a},e,f,g;for(f=0;f<d;f++)g=a[f].split("="),(e=z[g.shift()])&&(c=e(c,g));for(f=0;f<b;f++)c=x[f](c);return c}function g(a,e,f,g,h){var i=b(a),j=i.autoCallback;i.url.split(".").pop().split("?").shift(),i.bypass||(e&&(e=d(e)?e:e[a]||e[g]||e[a.split("/").pop().split("?")[0]]),i.instead?i.instead(a,e,f,g,h):(y[i.url]?i.noexec=!0:y[i.url]=1,f.load(i.url,i.forceCSS||!i.forceJS&&"css"==i.url.split(".").pop().split("?").shift()?"c":c,i.noexec,i.attrs,i.timeout),(d(e)||d(j))&&f.load(function(){k(),e&&e(i.origUrl,h,g),j&&j(i.origUrl,h,g),y[i.url]=2})))}function h(a,b){function c(a,c){if(a){if(e(a))c||(j=function(){var a=[].slice.call(arguments);k.apply(this,a),l()}),g(a,j,b,0,h);else if(Object(a)===a)for(n in m=function(){var b=0,c;for(c in a)a.hasOwnProperty(c)&&b++;return b}(),a)a.hasOwnProperty(n)&&(!c&&!--m&&(d(j)?j=function(){var a=[].slice.call(arguments);k.apply(this,a),l()}:j[n]=function(a){return function(){var b=[].slice.call(arguments);a&&a.apply(this,b),l()}}(k[n])),g(a[n],j,b,n,h))}else!c&&l()}var h=!!a.test,i=a.load||a.both,j=a.callback||f,k=j,l=a.complete||f,m,n;c(h?a.yep:a.nope,!!i),i&&c(i)}var i,j,l=this.yepnope.loader;if(e(a))g(a,0,l,0);else if(w(a))for(i=0;i (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0];var j=d.createElement(s);var dl=l!='dataLayer'?'&l='+l:'';j.src='//www.googletagmanager.com/gtm.js?id='+i+dl;j.type='text/javascript';j.async=true;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-M677548'); Skip to main content Home About Submit ALERTS / RSS Search for this keyword Advanced Search New Results Starvation transforms signal encoding in C. elegans thermoresponsive neurons and suppresses heat avoidance via bidirectional glutamatergic and peptidergic signaling Saurabh Thapliyal , View ORCID Profile Dominique A. Glauser doi: https://doi.org/10.1101/2025.07.17.665269 Saurabh Thapliyal 1 Department of Biology, University of Fribourg , Chemin du Musée 10, 1700 Fribourg, Switzerland Find this author on Google Scholar Find this author on PubMed Search for this author on this site Dominique A. Glauser 1 Department of Biology, University of Fribourg , Chemin du Musée 10, 1700 Fribourg, Switzerland Find this author on Google Scholar Find this author on PubMed Search for this author on this site ORCID record for Dominique A. Glauser For correspondence: dominique.glauser{at}unifr.ch Abstract Full Text Info/History Metrics Preview PDF ABSTRACT Animals must continuously adapt their behavioral outputs in response to changes in internal state, including nutritional state. Here, we show that starvation induces a profound and progressive suppression of thermonociceptive behavior in Caenorhabditis elegans . The thermoresponsive sensory neurons AWCs mediate robust heat-evoked reversals over a broad range of stimulus intensities via glutamate and FLP-6 neuropeptide signaling, each covering distinct heat intensity ranges. After six hours of food deprivation, heat-evoked reversal responses are nearly abolished, independently of any external food odor cues. Prolonged food deprivation triggers a switch in AWC heat-evoked activity patterns, transitioning from a predictable, stimulus-locked response mode to a heterogeneous and stochastic regime. This switch relies on ASI neurons, proposed to work as internal state-sensing neurons. INS-32 and NLP-18 neuropeptide signals from ASI switch from a reversal-promoting to a reversal-inhibiting effect. Glutamatergic transmission from non-AWC neurons is also engaged to suppress reversals. Our findings define a circuit logic by which nociceptive responsiveness gating by internal nutritional state is linked to dynamic modulation of sensory neuron activity patterns and orchestrated by bidirectional glutamatergic and neuropeptidergic signals. More broadly, this study illustrates how sensory systems integrate metabolic information to prioritize behavioral outputs under changing physiological conditions, providing mechanistic insight into the plastic coupling between sensation, internal state, and action selection. INTRODUCTION To ensure survival, animals must detect and avoid noxious stimuli, such as harmful chemicals, toxic gases, or extreme temperatures. These avoidance behaviors, often categorized as nociceptive, are conserved across phyla and essential for minimizing damage and guiding appropriate behavioral responses. Like most animals studied so far, the nematode Caenorhabditis elegans , can produce robust innate escape behaviors and modulate these responses according to external and internal regulatory cues [ 1 – 4 ]. Many genes involved in mammalian pain perception and plasticity—such as the Transient Receptor Potential channels, CaM kinase and Calcineurin—are also implicated in worms, underscoring the evolutionary conservation of nociceptive pathways and the broad interest of the C. elegans model [ 5 – 9 ]. C. elegans is a small ectotherm, whose temperature equilibrates almost instantly with its surroundings. It can grow in a 15 to 25°C range. C. elegans produces robust avoidance behaviors in response to noxious temperature (which can be defined as temperature above 26°C) or to fast-raising thermal stimuli even below 26°C [ 10 ]. Upon acute thermal stimulation, forward-moving worms respond to head-targeted or whole animal heating by initiating backward locomotion (reversal event) and to tail-targeted heating by accelerating their forward locomotion [ 11 ]. Several thermo-responsive neurons have been characterized (see [ 12 ] for a review). Among these neurons, AFD neurons are the best characterized primary thermosensory neurons responding to temperature changes and mediating both thermotaxis in response to innocuous thermal cues and noxious heat avoidance response [ 13 ]. FLP neurons are tonic thermosensors whose activity level continuously reflects the current temperature, and which regulate animal speed and reorientation maneuvers [ 14 , 15 ]. AWC neurons are polymodal sensory neurons responding to olfactory cues and to temperature in a context-dependent manner [ 16 – 18 ]. The pair of AWC sensory neurons asymmetrically differentiate into AWC ON and AWC OFF , which express specific markers and respond either similarly or differentially depending on the stimulus type [ 19 ]. Regarding AWC response to temperature change, both deterministic (stimulus-locked calcium elevations upon warming [ 18 ]), and stochastic responses, whose frequency can be modulated by warming [ 20 ], have been reported depending on experimental conditions. In addition, extremely powerful IR-laser based pulses—causing a 10°C elevation from 23 to 33°C within tens of milliseconds— were shown to trigger subtype-specific response: calcium elevation in AWC ON and calcium decrease in AWC OFF [ 21 ]. ASI sensory neurons have also been reported to respond to change in temperature in the innocuous range [ 22 ], but their implication in noxious-heat response is not known. Neuromodulators, including neuropeptides and monoamines, play a central role in reconfiguring behavioral responses to sensory inputs based on context [ 15 , 23 , 24 ]. In particular, neuropeptides have been shown to drive behavioral plasticity across a range of paradigms in C. elegans , including feeding-dependent changes in locomotion and sensory responsiveness as a response to changes in the animal’s internal physiological and metabolic states [ 25 – 27 ]. A reduction of nociceptive sensitivity or responsiveness during prolonged starvation could in principle help worms travel across harsher environments in order to find new food sources. Consistent with this potential ecological advantage, food deprivation-dependent reduction has been shown for the response to high osmolarity and chemical repellents [ 1 , 28 ]. Examples of plasticity in the thermonociceptive response of C. elegans are so far essentially limited to the down-regulation of noxious heat avoidance in response to persistent exposure to moderately noxious heat level (28°C) or repeated heat stimulations [ 9 , 29 – 31 ]. The impact of prolonged starvation and the contribution of neuromodulation in the context-dependent regulation of thermonociceptive behaviors is largely unknown. Here, we investigate how feeding state modulates heat avoidance behavior in C. elegans . We show that prolonged starvation significantly suppresses thermonociceptive responses, a plasticity not driven by external chemosensory cues but caused by nutrient availability. We identify a critical role for the AWC sensory neurons in mediating heat-evoked escape responses, and for the ASI neuroendocrine neurons in modulating these responses under starvation. Our data show that AWC neurons employ both glutamate and the neuropeptide FLP-6 to mediate avoidance, with distinct contributions from AWC ON and AWC OFF subtypes. Under early food deprivation, AWC responses to heat are stereotyped and excitatory, but under prolonged starvation, these responses become variable, reflecting a shift from deterministic to stochastic encoding. This shift depends on the ASI neurons, which modulate heat-evoked response via NLP-18 and INS-32 neuropeptides. Additionally, our findings suggest that glutamatergic signaling from non-AWC sources also contribute to the suppression thermonociception following starvation. Together, our results suggest a neuromodulatory mechanism by which internal nutritional state reconfigures nociceptive behavior. This demonstrates that even hard-wired escape responses are not immune to physiological context, and highlights a broader principle: survival strategies in simple animals balance external threats against internal needs through circuit-level plasticity. RESULTS Starvation downregulates thermonociceptive responses in C. elegans To assess how the feeding state modulates thermonociceptive behavior in C. elegans , we compared responses across different durations of food deprivation ( Figure 1A ). Although fed animals showed high sensitivity to noxious heat, they also displayed an elevated baseline of spontaneous reversals, which limited their utility as a control group ( Figure 1B ). A 1-hour off-food condition reduced spontaneous reversals and led to a mild attenuation of heat-evoked responses at low stimulus intensities, while responses to stronger stimuli remained comparable to those of fed animals. Download figure Open in new tab Figure 1 Starvation-dependent thermonociceptive plasticity in C. elegans A . Schematic of the experimental procedure to quantify the impact of food deprivation on thermonociception in C. elegans adult hermaphrodites. Spontaneous and heat-evoked reversals were quantified in fed animals on food (Fed) or off food after 1,2,3, and 6 hr of food deprivation. Spontaneous reversals were measured as baseline reversal rate prior to any stimuli (0 W) and heat-evoked reversals were measured during a series of 4-s heat pulses at 100, 200, 300 and 400 W, respectively, delivered with an interstimulus interval of 20 s. B - C . Impact of food deprivation on thermonociceptive response, showing progressive attenuation of heat-evoked reversal response in the course of a 6-hr experiment. Results as average fraction of reversing animals (%) quantified in N ≥ 6 assays, each scoring at least 50 worms. Error bars: S.E.M. The same dataset is presented as heat dose-response curves (B) and as time-course of the heat-evoked response decrease at each heating level (C). Spontaneous reversal rate corresponds to the baseline reversal response in the absence of heating stimuli (0 W). D. Effect of prolonged starvation (off-food for 6 hr) in the presence or absence of food odor during the food-deprivation period, indicating that external food odor cues cannot prevent the response reduction. **, p> .01 versus the early food deprivation condition (off-food 1hr), by Holm-Bonferroni post-hoc tests. Prolonged food deprivation led to a striking progressive reduction in thermonociceptive responses, with responses after 6 hours of starvation approaching baseline spontaneous reversal rates ( Figure 1B and C ). This suggests a robust inhibition of nociceptive behavior. To determine whether this attenuation was due to the absence of nutrients or chemosensory cues, we conducted similar starvation experiments in the presence of food odor ( Figure 1D ). The reduction in thermonociceptive response persisted, indicating that the effect is driven by the internal starvation state rather than external olfactory input. Based on this observation, we focused subsequent analyses on dissecting the circuit and molecular underpinnings of starvation-dependent plasticity, using the 1-hour and 6-hour off-food conditions as representative of early food deprivation and prolonged starvation, respectively. Distinct roles of AWC and ASI neurons in heat-evoked response and starvation-dependent plasticity To identify the neural substrates underlying thermonociceptive behavior and its modulation by starvation, we genetically ablated candidate thermosensory neurons ( Figure 2 ). Surprisingly, ablation of AFD—the canonical thermosensory neuron—had no significant effect under either 1h or 6h food deprivation ( Figure 2 Supplement 1 ). Simultaneous ablation of AFD and FLP neurons induced an increase in spontaneous reversals, but only a mild reduction in heat-evoked responses and left starvation-dependent plasticity largely intact, suggesting a minor contribution of these neurons ( Figure 2 Supplement 1 ). By contrast, ablation of AWC or ASI neurons had dramatic effects. Removal of AWC nearly abolished heat-evoked reversal behavior across all stimulus intensities and timepoints ( Figure 2B and D ), confirming its essential role in mediating the thermonociceptive response. Notably, in AWC-ablated animals, the response level was unaffected by starvation, suggesting that AWC might also be required for the expression of starvation-dependent plasticity. In contrast, ASI ablation had almost no effect under early food deprivation but almost entirely suppressed the starvation-induced reduction in heat-evoked reversals observed after prolonged starvation ( Figure 2C and D ). This demonstrates that ASI is specifically required for starvation-dependent modulation of thermonociceptive behavior. Download figure Open in new tab Figure 2-supplement 1 Heat-evoked reversal upon early food deprivation and starvation-dependent plasticity are largely intact in AFD and FLP-ablated animals Impact of the genetic ablation of candidate thermo-responsive neurons on thermonociceptive response and starvation-dependent plasticity. A-C Comparison of heat-evoked reversals after early food deprivation (off-food 1hr) and starvation (off-food 6 hr) in wild type and in transgenic animals with caspase-mediated ablation of indicated neurons. Results are presented as average +/- S.E.M. *, p<.05, and * *, p<.01 versus corresponding heat level in the early food deprivation condition, by Bonferroni post-hoc tests. E Comparison for the 400 W heating level across the three genotypes presented in panel A to C. Bars as average, dots as individual assay scores, and error bars as S.E.M. ##, p<.01 between early food deprivation and prolonged starvation for each genotype; ** , p<.01 versus wild type (N2) at the corresponding time point, by Holm Bonferroni post-hoc tests. The total number of assays analyzed per condition, each scoring at least 50 worms, are indicated in panel D. Download figure Open in new tab Figure 2 AWC mediates heat-evoked reversals upon early food deprivation and ASI mediates thermonociceptive plasticity upon starvation Impact of the genetic ablation of AWC and ASI sensory neurons on thermonociceptive response and starvation-dependent plasticity. A-C Comparison of heat-evoked reversals after early food deprivation (off-food 1hr) and prolonged starvation (off-food 6 hr) in wild type and in transgenic animals with caspase-mediated ablation of indicated neurons. Results are presented as average +/- S.E.M. *, p<.05, and * *, p<.01 versus corresponding heat level in the early food deprivation condition, by Bonferroni post-hoc tests. D Comparison for the 400 W heating level across the three genotypes presented in panel A to C. Bars as average, dots as individual assay scores, and error bars as S.E.M. ##, p<.01 between early food deprivation and prolonged starvation for each genotype; ** , p<.01 versus wild type (N2) at the corresponding time point, by Holm Bonferroni post-hoc tests. The total number of assays analyzed per condition, each scoring at least 50 worms, are indicated in panel D. Together, these data show that, under our experimental conditions, AWC is the primary driver of heat-evoked reversals upon early food deprivation, while ASI neurons selectively mediate their suppression under prolonged starvation. AWC neurons mediate heat-evoked reversal via both glutamate and FLP-6 neuropeptides We next sought to define the molecular mechanisms by which AWC neurons mediate robust heat-evoked reversals in the early food deprivation condition. AWC neurons are glutamatergic and express several neuropeptides, including FLP-6, INS-22 and NLP-5 [ 32 , 33 ]. eat-4 mutants lacking the vesicular glutamate transporter EAT-4 exhibited strong impairments in heat-evoked responses at high stimulus intensities (300–400 W) and a reduction in spontaneous reversal rates ( Figure 3A ). flp-6 mutants displayed a marked deficit across a broad, 200–400 W stimulus range, while the impairment in ins-22 and nlp-5 mutants was less pronounced and more selectively affected the 200–300 W range of stimulus intensities ( Figure 3C and Figure 3-Supplement 1 ). This indicates that different communication molecules are used over different thermal ranges to mediate heat-evoked reversals, which is in line with previous genetic analyses having recurrently shown that multiple genetic pathways are recruited for different levels of heat [ 6 , 34 ]. Download figure Open in new tab Figure 3-Supplement 1 A-B Comparison of spontaneous (0 W) and heat-evoked reversals (100 to 400 W) after early food deprivation (off-food 1hr) in wild type, nlp-5(ok1981) and ins-22(ok3616) . Results are presented as average +/- S.E.M. *, p<.05 and * *, p<.01 versus wild type by Holm-Bonferroni post-hoc tests. The number of assays ( N ), each scoring at least 50 worms, were: wild type, N= 15; nlp-5 , N= 6; ins-22 , N= 6. Download figure Open in new tab Figure 3 Differential engagement of glutamate and FLP-6 neuropeptides by AWC ON and AWC OFF in the control of spontaneous and heat-evoked reversal at various heat levels A-D Comparison of spontaneous (0 W) and heat-evoked reversals (100 to 400 W) after early food deprivation (off-food 1hr) in wild type, eat-4(ky5) , flp-6(ok3056) and in transgenic animals with AWC subtype-specific rescue of eat-4 and flp-6 , respectively. Results are presented as average +/- S.E.M. * *, p<.01 versus wild type (A and C) and versus non-transgenic mutants (B and D) at respective heat levels, by Holm-Bonferroni post-hoc tests. The number of assays ( N ), each scoring at least 50 worms, were: wild type, N= 15; eat-4 , N= 6; flp-6 , N= 14; eat-4+[AWC OFF ::eat-4] , N= 6; eat-4+[AWC ON ::eat-4] , N= 9; flp-6+[AWC OFF ::flp-6] , N= 7; flp-6+[AWC OFF ::flp-6] , N= 8. E Visual model illustrating the specific contribution of AWC OFF and AWC ON to the regulation of spontaneous reversal, low heat-evoked reversal and high heat-evoked reversal, via the distributed action of glutamate and FLP-6 neuropeptide. Next, we focused on eat-4 and flp-6 mutants, showing the strongest phenotype, and carried out cell-specific rescue to demonstrate that AWC neurons represent a relevant source of glutamate and FLP-6 neuropeptides promoting heat-evoked reversals upon early food deprivation (off-food 1hr). Transgenic rescue experiments using either [AWC OFF ::eat-4] or [AWC ON ::eat-4] extrachromosomal array containing-lines showed that restoring eat-4 expression in either AWC ON or AWC OFF alone was sufficient to recover heat-evoked responses to near wild-type levels ( Figure 3B ). Interestingly, [AWC OFF ::eat-4] transgene not only restored responsiveness but also enhanced reversals at 100 W, potentially reflecting overexpression effects or altered signaling balance with other glutamatergic neurons. Additionally, spontaneous reversal rates were restored only by [AWC OFF ::eat-4] . A similar rescue approach for flp-6 expression in AWC revealed that only [AWC OFF ::flp-6] , not [AWC ON ::flp-6] , could rescue heat-evoked behavior, suggesting asymmetry in neuropeptidergic signaling ( Figure 3D ). Our data indicate that any one of the two AWCs might be sufficient to mediate a large part of the glutamate-dependent reversal response, but that AWC OFF and AWC ON might display some functional asymmetries, regarding the role of neuropeptides and the regulation of spontaneous reversal. To further address the role of AWC ON/OFF asymmetry, we examined nsy-1 mutants, developing with two AWC ON and nsy-7 , developing with two AWC OFF [ 35 , 36 ]. Both mutants exhibited reduced responses at high heat intensities, with nsy-1 also showing increased spontaneous reversals ( Figure 3-Supplement 2 ). Download figure Open in new tab Figure 3-Supplement 2 AWC subtype differentiation is partly required for proper heat-evoked reversal response after 1hr off food. A-B Comparison of spontaneous (0 W) and heat-evoked reversals (100 to 400 W) after early food deprivation (off-food 1hr) in wild type, nsy-1(ok593) , in which both AWCs differentiate as AWC ON and nsy-7(tm3080) , in which both AWCs differentiate as AWC OFF . Results are presented as average +/- S.E.M. *, p<.05 and * *, p<.01 versus wild type by Holm-Bonferroni post-hoc tests. The number of assays, each scoring at least 50 worms, were: wild type, N= 15; nsy-1 , N= 6; nsy-7 , N= 6. These results indicate that AWC neurons mediate thermonociceptive responses through both glutamatergic and FLP-6-dependent pathways, each covering distinct heat intensity ranges ( Figure 3E ). While either AWC subtype is sufficient for glutamatergic signaling, FLP-6 neuropeptide function appears more dependent on AWC OFF identity. Starvation alters the nature of AWC heat responses from deterministic to stochastic To investigate if and how starvation modulates AWC activity at the cellular level, we recorded heat-evoked calcium dynamics in AWC ON and AWC OFF neurons using YC2.3 cameleon-expressing transgenic lines. We used a microfluidic setup to deliver defined thermal stimuli. From a baseline at 20°C, four stimuli reaching 22, 24, 26 and 28°C, respectively, were sequentially delivered, corresponding approximately to the temperatures reached in the heat-evoked behavioral analysis ( Figure 3 ). We examined responses under both early food deprivation and prolonged starvation conditions. In Figure 4A and B , we report average traces and individual traces as heat maps. Individual traces are essential to visualize the stochastic component of the response in some neurons and we clustered traces as ‘calcium up’ (traces showing consistent up-regulation after 24, 26 and 28° stimuli), ‘variable’ (traced showing a mix of up and down regulation) and ‘calcium down’ (traces showing consistent down-regulation after 24, 26 and 28° stimuli). The ‘calcium down’ traces were often, but not always, followed by a ‘rebound’ upregulation. Download figure Open in new tab Figure 4 Starvation reconfigures AWC heat-evoked response from a mostly deterministic to a stochastic activity mode A-B Calcium activity in AWC OFF (left) and AWC ON (right) in response to a series of four thermal up-steps. Upper plots show the average traces, lower heat maps show individual neuron traces, in the early food deprivation (off-food 1hr) and prolonged starved (off-food 6hr) conditions. C-D From the same dataset as in A-B, average traces showing the dynamics of calcium up or calcium down response types with similar amplitude and globally comparable shapes. Upon early food-deprivation, both AWC neuron subtypes responded with a stereotyped, intensity-dependent calcium increase (“calcium up”) in most animals (45/56, 80% for AWC OFF and 37/49, 77% for AWC ON ). The remaining traces showed either mixed (“variable”) or “calcium down” profiles. After prolonged starvation, this response pattern shifted dramatically: the majority of traces became variable or showed consistent calcium down-regulation (17/23, 74% for AWC OFF and 14/17, 82% for AWC ON , both changes being statistically significant by Fisher’s exact test: p =1.3E-5 and p= 7.6E-5, respectively). This shift was reflected in the average traces ( Figure 4A and B ) as a decreased peak amplitude and rightward shift. But the modification of the average trace was largely caused by the redistribution in response types: the dynamic of individual calcium up and calcium down traces remaining similar in each condition ( Figure 4 C and D). Therefore, AWC neurons, which under early food deprivation respond consistently to heat, enter a heterogeneous and less predictable response mode under prolonged starvation. In summary, starvation does not simply attenuate AWC calcium responses; it fundamentally alters their dynamics, shifting from a largely deterministic excitation profile to a heterogeneous regime characterized by decreased and variable responses. We speculate that this transformation in thermal encoding might underlie the behavioral plasticity observed during starvation. ASI is required to shift AWC activity from deterministic to stochastic modes upon starvation Because ASI neurons are required for the starvation-dependent thermonociceptive plasticity, dispensable for noxious heat-evoked reversal response, and have been previously shown to signal the feeding state of the animal [ 37 ], we hypothesized that ASI neurons might play a modulatory role to mediate the starvation impact on AWC activity patterns. To test this hypothesis, we recorded AWC ON and AWC OFF activity in ASI-ablated animals, which we found to lack starvation-evoked plasticity ( Figure 2C ). In the early food-deprivation condition, 1hr off-food, ASI ablation produced no noticeable difference in AWC calcium activities (compare Figure 4 with 5). Strikingly different from the situation in animals with intact ASI ( Figure 4 ), starvation after 6hr off-food produced no noticeable effect in ASI-ablated animals, neither for AWC ON , nor for AWC OFF ( Figure 5 ). We conclude that the starvation-dependent shift in AWC activity from a deterministic to stochastic pattern is mediated by the neuromodulatory neurons ASI. Download figure Open in new tab Figure 5 ASI ablation prevents AWC activity pattern reconfiguration upon starvation ( A-B ) Calcium activity in AWC OFF (A) and AWC ON (B) in response to a series of four thermal up-steps in ASI-ablated animals. Upper plots show the average traces, lower heat maps show individual neuron traces, in the early food deprivation (off-food 1hr) and prolonged starved (off-food 6hr) conditions. The starvation impact seen in animals with intact ASI ( Figure 4 ) is absent when ASI is ablated. Starvation-evoked thermonociceptivce plasticity is promoted by ASI-expressed neuropeptides, including NLP-18 and INS-32, and modulated by glutamatergic signaling To elucidate the molecular signaling pathway underlying starvation-evoked thermonociceptive plasticity involving the AWC and ASI sensory neurons, we investigated the role of candidate neurotransmitters expressed in AWC and ASI, respectively. First, we tested whether starvation-dependent plasticity was preserved in eat-4 and flp-6 mutant backgrounds. Even if the heat-evoked response upon early food-deprivation was reduced relative to wild type in flp-6 mutants, a significant further decline was seen after prolonged starvation ( Figure 6B ). These results indicate that starvation-dependent plasticity can operate independently of FLP-6. In contrast, eat-4 mutants displayed markedly elevated heat-evoked responses after prolonged starvation, even exceeding the response level seen in the early food deprivation condition ( Figure 6C ). This potentiated response could not be rescued by expressing eat-4 selectively in either AWC OFF or AWC ON neurons ( Figure 6D ). Interestingly, AWC OFF -specific rescue produced a further potentiation of heat-evoked reversal response to high heat stimuli ( Figure 6D , 300 and 400 W), aggravating the phenotype of eat-4 mutants. Download figure Open in new tab Figure 6 Bidirectional glutamate signaling actions modulate heat-evoked reversals following starvation A-C Comparison of heat-evoked reversals after early food deprivation (off-food 1hr) and prolonged starvation (off-food 6hr) in wild type, eat-4(ky5) , flp-6(ok3056) . D Analysis of transgenic animals with AWC subtype-specific rescue of eat-4 after prolonged starvation (off-food 6hr). Results are presented as average +/- S.E.M. * *, p<.01 between the two food-deprivation time points (A-C) and versus non-transgenic mutants (D) at respective heat levels, by Holm-Bonferroni post-hoc tests. The number of assays ( N ), each scoring at least 50 worms, were: wild type, N= 15; eat-4 , N= 6; flp-6 , N= 14; eat-4+[AWC OFF ::eat-4] , N= 6; eat-4+[AWC ON ::eat-4] , N= 9. E Visual model illustrating the bidirectional effect of glutamatergic signaling from AWC OFF and from unidentified non-AWC neurons (other). Red: reversal-supressing pathway; Green: reversal-promoting pathway. These results are consistent with a model in which glutamatergic signaling regulates heat-evoked reversals in starved animals via two bidirectional drives ( Figure 6E ). On the one hand, glutamatergic signalling—originating from AWC OFF —up-regulates reversals in response to high heat stimuli, thus contributing to prevent starvation-induced thermonociceptive plasticity. On the other hand, glutamatergic signaling—originating from neurons other than AWC— down-regulates reversals over a broad range of heat intensities, thus promoting starvation-induced thermonociceptive plasticity. The latter glutamatergic signaling effect seems to be more dominant. Second, since ASI is required for starvation-evoked plasticity but does not release classical neurotransmitters, we hypothesized that its function is mediated by neuropeptidergic signaling. We therefore screened for defects in starvation-dependent plasticity in mutants for neuropeptide genes known to be expressed in ASI: ins-4, ins-6, ins-32, and nlp-18 [ 32 , 33 , 38 , 39 ] . ins-4 mutants exhibited normal plasticity, with robust responsiveness under early food deprivation and significantly reduced responses after prolonged starvation ( Figure 7A ). Mutants for ins-6, ins-32, and nlp-18 all showed reduced responsiveness in the early food deprivation condition, but abnormally elevated responses after prolonged starvation ( Figure 7A ). This phenotype was qualitatively similar to the potentiation phenotype of eat-4 mutants ( Figure 6C ). We performed further analyses with ins-32 and nlp-18 mutants, since they produced the most significant potentiation over a large range of heat intensities. To confirm whether ASI is a relevant source of INS-32 and NLP-18 neuropeptides, we conducted ASI-specific rescue experiments in ins-32 and nlp-18 mutants. In ins-32 mutant background, ASI-specific expression of ins-32 produced a strong rescue effect, significantly restoring reversal response in early food-deprive animals ( Figure 7B ) and significantly reducing heat-evoked reversal response under the starvation condition ( Figure 7C ). In nlp-18 mutant background ASI-specific expression of nlp-18 did not restore normal responsiveness after 1 hr off-food, but partially restored the response decrease after 6 hr of starvation. These results indicate that ASI is a functionally relevant source of both INS-32 and NLP-18 to promote starvation-evoked thermonociceptive inhibition, although they do not exclude the possibility of contributions from other sources ( Figure 7F ). Furthermore, INS-32 from ASI and NLP-18 from additional neurons might promote reversals upon early food deprivation. Download figure Open in new tab Figure 7 Starvation reconfigures neuropeptidergic signaling by ASI A Comparison of heat-evoked reversals after early food deprivation (off-food 1hr) and prolonged starvation (off-food 6hr) in wild type, ins-4(ok3534), ins-6(tm2008), nlp-18(ok1557) and ins-32(tm6109) . *, p<.05, and * *, p<.01 between the two food deprivation time points, by Holm Bonferroni post-hoc tests. #, p<.05, and ##, p<.01 versus wild type (N2) at the corresponding time point, by Holm Bonferroni post-hoc tests. B-E Impact of transgenic rescue in ins-32 (B-C) and nlp-18 (D-E) background. Two-way ANOVA showing no significant heating power x genotype interaction, but a significant genotype main effect, post-hocs tests were conducted on the genotype factor only. Indicated p values were corrected with Holm Bonferroni correction. F Model of the bidirectional actions and the sources for NLP-18 and INS-32 neuropeptides in the modulation of heat-evoked reversal. Red: reversal-suppressing pathway; Green: reversal-promoting pathway. Collectively, our results ( Figure 6 and 7 ) show that starvation-dependent thermonociceptive plasticity is orchestrated by multiple opposing signaling pathways in which neuropeptides and glutamate signals from different neurons produce context-dependent, bidirectional effects. DISCUSSION Our study reveals that starvation profoundly modulates thermonociceptive behavior in C. elegans by engaging distinct neurons, altering neural response dynamics, and mobilizing opposing neuromodulatory pathways. This behavioral plasticity, manifesting as a progressive attenuation of heat-evoked reversals under prolonged food deprivation, depends on a shift in the internal state that is not rescued by food-associated olfactory cues. By dissecting the underlying circuits and signaling mechanisms, we uncover two key regulatory nodes involving AWC and ASI neurons, which work in order to integrate thermal and nutritional cues into an adaptive behavioral output, as depicted in the visual model in Figure 8 . Download figure Open in new tab Figure 8 Visual model of the cellular and molecular signaling pathways mediating and modulating heat-evoked reversals according to feeding state A Situation upon early food deprivation (off-food 1hr). The two AWC neurons produce mostly deterministic calcium elevations in response to heat stimuli and make a major contribution to heat-evoked reversals. Glutamate signaling from AWC ON and AWC OFF , as well as FLP-6 neuropeptide signaling from AWC OFF mediates heat-evoked reversals. INS-32 neuropeptide from ASI neurons, as well as NLP-18 neuropeptides from an unidentified source, also promote heat-evoked reversals. B Situation following prolonged starvation (off-food 6hr). Starvation causes several functional changes. First, AWC calcium activity pattern switches from a deterministic mode to a stochastic mode, with a mix of calcium elevations, calcium decreases and variable responses; this effect is mediated by ASI. Second, INS-32 and NLP-18 neuropeptides switch from a reversal-promoting effect to a reversal-suppressing effect; for INS-32, ASI remains a relevant peptide source, whereas for NLP-18 ASI becomes a relevant peptide source. Third, glutamatergic signaling switches from a mostly reversal-promoting effect to a reversal-suppressing effect; this switch is associated with different glutamate sources (in AWC and non-AWC neurons, respectively). Of note, residual reversal response upon starvation might be mediated by FLP-6 and glutamate from AWC OFF . In summary, our findings highlight a complex reconfiguration of the thermoresponsive circuit following starvation, which includes thermosensory encoding change and complex neuromodulation using bidirectional signaling molecules that produce reversal-promoting (green pathways) or reversal-suppressing effects (red pathways) in a context-dependent manner. AWC neurons are central drivers of heat-evoked reversal behavior via glutamate and neuropeptides Our findings confirm that AWC sensory neurons are critical mediators of thermonociceptive behavior. Previous experiments carried out with extreme heating powers (10 °C raise within tens of milliseconds, [ 21 ]) had shown differential responsiveness in the two AWCs subtypes and a large behavioral impact was found in mutants affecting AWC asymmetries. The heating intensity range used in the present study (∼0.5 to 2°C per second) triggered a similar withdrawal response, which almost entirely relied on the presence of intact AWC neurons. However, under our experimental conditions, we did not find major differences between AWC ON or AWC OFF subtypes in terms of calcium dynamics, nor did mutations affecting their asymmetry produce radical effects. Therefore, noxious heat-evoked activity in AWC varies widely according to context, which is in line with previous literature [ 18 , 20 , 25 ]. Interestingly, the role of AWC is distinct from that of AFD and FLP neurons, which are canonically linked to thermosensation and nociception [ 5 , 14 , 40 , 41 ], but contribute only modestly to heat-evoked behavior in our assays conditions with between 1 and 6 hrs of food deprivation. We further demonstrate that AWC neurons use both glutamatergic and neuropeptidergic signals to encode heat intensity, with glutamate (via EAT-4) primarily driving responses to stronger stimuli and the FLP-6 neuropeptide acting over a broader thermal range. Functional asymmetry between AWC ON and AWC OFF emerges in our rescue experiments, with AWC OFF more effective in restoring heat-evoked behavior, particularly through FLP-6. This suggests that AWC OFF may have privileged access to neuropeptidergic regulatory machinery or downstream targets, although glutamatergic signaling appears largely redundant across AWC subtypes. Together with previous findings, our results refine our appreciation of how AWC responds to heat and how developmental asymmetries might modulate aversive response to thermal cues over a very broad intensity range. Starvation reshapes AWC responses from deterministic to stochastic A key observation of this work is that prolonged starvation transforms heat-evoked AWC calcium responses from a stereotyped, intensity-dependent activation pattern to a heterogeneous, less predictable regime. This shift is not merely a quantitative attenuation but a qualitative reorganization of response states, including frequent calcium downregulation or variable traces, which in the same animal can comprise both calcium up- and down-regulation of calcium levels during a single stimulus train. We speculate that this transition from deterministic to stochastic response profiles reflects a fundamental reconfiguration of sensory processing under prolonged nutrient deprivation. In an early food-deprived state, AWC neurons may signal heat intensity in a consistent and reliable manner to promote aversion. Under prolonged starvation, however, dampened and variable AWC responses may bias the animal away from escape behaviors, thus prioritizing food-seeking over threat avoidance. This state-dependent reconfiguration may serve as a flexible strategy to balance risk avoidance and metabolic needs, as elaborated below. ASI neurons modulate AWC dynamics and promote plasticity via neuropeptides Our data demonstrate that ASI neurons are dispensable for baseline thermonociceptive responses but essential for starvation-induced behavioral plasticity. Ablation of ASI fully abolished the starvation-dependent attenuation of heat-evoked reversals and prevented the stochastic shift in AWC calcium dynamics. These results suggest that ASI gates the modulation of AWC activity based on internal nutritional state. ASI might also modulate the circuit downstream of AWC. Interestingly, in two previous studies, starvation-evoked down-regulation of AWC-dependent thermotactic behavior was intact when ASI was either transiently or chronically inhibited [ 39 , 42 ]. Therefore, starvation most likely uses a different circuitry to modulate noxious-heat evoked reversal than for thermotaxis modulation. We further identify two ASI-expressed neuropeptides, NLP-18 and INS-32, as relevant mediators of this plasticity. Mutants for the corresponding pro-neuropeptide genes displayed abnormal behavioral adaptation to starvation, and transgenic expression of either peptide in ASI partially rescues the plasticity defect. ASI was previously shown to mediate starvation-evoked phenotypic plasticity regarding developmental trajectories—via TGFbeta and the insulin-like peptide DAF-28 [ 43 , 44 ]—, food-seeking exploration in starved larvae - via NLP-24 opioid-like neuropeptide [ 45 ], the curvature taken during head-touch evoked escape response, via NLP-18 [ 46 ], and ASH-mediated octanol avoidance response-via multiple NLP neuropeptides [ 47 ]. Our findings now add context-dependent aversive thermosensory behavior regulation to the growing list of satiety signaling and stress integration-related functions regulated by ASI neurons. It remains to be determined how ASI integrates systemic cues of metabolic status and how its neuropeptidergic outputs interact with AWC-neural pathway at the synaptic or circuit level to regulate noxious heat avoidance. Opposing neuromodulatory influences shape behavioral flexibility in order to balance protection and exploration strategies The balance between starvation-induced suppression and preservation of thermonociceptive behavior appears to be controlled by a set of signaling molecules, whose effect can be bidirectional, operating in a context-dependent manner. Upon early food deprivation, neuropeptides, including INS-32 released from ASI and NLP-18 from an unidentified source, as well as glutamatergic signals from AWC neurons promote thermonociceptive behaviors ( Figure 8A ). Upon prolonged starvation, the same signaling molecules can produce the opposite effect and suppress this behavior ( Figure 8B ). For NLP-18 and glutamate the differential effect is associated with a potentially different source, e.g., non-AWC neurons for glutamate. For INS-32, our cell-specific rescue experiment suggests that ASI is a functionally relevant source in the two contexts. However, we cannot rule out the implication of additional neurons, nor an overexpression effect. While additional studies will be needed to decipher the context-dependent mode of action of each of these signaling molecules, our findings suggest a regulatory architecture in which bidirectional neuromodulatory signals integrate metabolic context with sensory drive to determine behavioral priorities. Rather than globally silencing the thermonociceptive pathway, starvation might well reconfigure it through a layered combination of neuronal state shifts, circuit-level inhibition, and peptide-based tuning. This complexity may afford the animal greater flexibility in selecting context-appropriate responses under competing environmental and internal pressures. From an ecological and evolutionary perspective, the downregulation of nociceptive responses during prolonged starvation likely reflects a strategic shift in behavioral priorities. In the face of acute noxious stimuli, animals typically favor rapid escape to minimize injury—a protective response. However, under prolonged food deprivation, such protection may come at the cost of missed opportunities for locating food. In this context, a heightened aversive response could lead to excessive avoidance of mildly threatening environments that may nevertheless contain nutritional resources. In addition, because worm exploration strategies rely on modulating locomotion speed, the duration of forward locomotion bouts and the frequency of re-orientation events, often associated with reversals, the down-regulation of reversal response is directly relevant to the rate of animal dispersion in the environment [ 48 , 49 ]. By reducing the sensitivity or reliability of nociceptive pathways— particularly through modulating AWC output— C. elegans may adopt a more exploratory behavioral mode, tolerating greater risk to increase the chances of finding food. This trade-off between protection and exploration mirrors similar state-dependent shifts observed in other species [ 50 , 51 ] suggesting a conserved strategy wherein internal metabolic needs dynamically reshape threat evaluation and behavioral responses. METHODS C. elegans maintenance and strains list C. elegans strains were maintained according to standard techniques on nematode growth medium (NGM) agar plates seeded with OP50. Animal synchronization was made by treating gravid adults with standard hypochlorite-based procedure. File S1 includes a list of strains used in the present study. Cloning and transgenesis DNA prepared with a GenElute HP Plasmid miniprep kit (Sigma) was microinjected in the gonad to generate transgenic lines according to a standard protocol [ 52 ]. Promoter-containing Entry plasmids (Multi-site Gateway slot 1) were constructed by PCR using N2 genomic DNA as template and primers flanked by attB4 and attB1r recombination sites; the PCR product being cloned into pDONR-P4-P1R vector (Invitrogen) by BP recombination. Coding sequence-containing Entry plasmids (Multi-site Gateway slot 2) were constructed by PCR using N2 cDNA as template and primers flanked by attB1 and attB2 recombination sites; the PCR product being cloned into pDONR_221 vector (Invitrogen) by BP recombination. Expression plasmids for transgenesis were created through LR recombination reactions (Gateway LR Clonase, Invitrogen) as per the manufacturer’s instructions.DNA prepared with a GenElute HP Plasmid miniprep kit (Sigma) was microinjected in the gonad to generate transgenic lines according to a standard protocol (Evans, 2006). File S1 includes a list of plasmids and primers used in this study. Behavioral assays Preparation of worms All the behavioral experiments were performed in young adult animals cultivated at 20°C. For the Fed condition, 80 animals were transferred to a NGM plate fully covered with OP50 bacterial lawn 18 hours before the experiment. For starved condition, fed animals were washed 3 times in 1.5 mL collection tubes with M9 (pre-equilibrated at the growth temperature of worms) to remove OP50. During washes, worms were left to settle to the bottom of the tubes by gravity. About 80 animals were then plated on unseeded NGM plates with a drop of M9 and left to air dry for 5 min. Duration of starvation was considered from the time of the start of the wash. During starvation, animals were kept in the incubator at 20°C. Heat-stimulation protocol Heat stimulation was delivered using previously described INFERNO system [ 30 ]. The stimulation program consisted of a baseline period of 40 s without any heat stimulation (to determine spontaneous reversal rate), 4 s with 100 W heating (1 IR lamp turned on), 20 s of interstimulus interval (ISI), 4 s with 200 W heating (2 lamps turned on), 20 s of ISI, 4 s with 300 W heating (3 lamps turned on), 20 s of ISI and 4 s with 400 W heating (4 lamps turned on) as previously described. The peak temperatures reached at the surface of the plate were ∼22, ∼24, ∼26 and ∼28°C, for each of the four heating powers, respectively. Movie recording and analysis During the stimulation program, worm plates were filmed using a DMK 33U×250 camera and movies acquired with the IC capture software (The Imaging Source), at a 1600×1800 pixel resolution, at 8 frames per second, and the resulting. AVI file was encoded as Y800 8-bit monochrome. Behavioral recordings were analyzed using the Multi-Worm Tracker 1.3.0 (MWT) [ 53 ]. A custom Python script was used to flag reversal events and report the frame during which they occurred. The movie time course was separated into 4-s bins and the fraction of animals reversing in each bin was extracted as the primary output for subsequent analyses. Calcium imaging Calcium imaging was performed using a Leica DMI6000B inverted epifluorescence microscope equipped with a HCX PL Fluotar L40x/0.60 CORR dry objective, a Leica DFC360FX CCD camera, an EL6000 light source, and equipped with fast filter wheels for FRET imaging (excitation filter: 427 nm (BP 427/10); emission filters 472 (BP 472/30) and 542 nm (BP 542/27) [ 14 ]. Calcium levels in AWC ON and AWC OFF neurons were monitored using cameleon YC2.3 sensor. Animals cultivated at 20°C were glued, maintained at 20°C for 90 s of baseline imaging acquisition and subjected to 30s heat stimulation at 22°C, 24°C, 26°C and 28°C using CherryTemp microfluidic system by Cherry Biotech, with 60s ISI. Imaging YFP/CFP ratio of the YC2.3 cameleon indicator was used to analyze relative changes in response to short-lasting stimuli. The imaging was performed 1 h and 6 h after food deprivation. Statistical analyses ANOVAs and post hoc tests, using Bonferroni–Holm correction, were conducted using GraphPad Prism. Replicate numbers are defined in the Figures. COMPETING INTERESTS No competing interests declared ACKNOWLEDGEMENTS We are grateful to Lisa Schild and Laurence Bulliard for expert technical support, to Aurore Jordan for the cloning of AWC-specific promoter plasmids and for the participation in calcium trace acquisition. Some strains were provided by the CGC, which is funded by NIH Office of Research Infrastructure Programs (P40 OD010440). Some strains were provided by NBRP, which is funded by the Japanese government. The study was supported by the Swiss National Science Foundation (BSSGI0_155764, PP00P3_150681, and 310030_197607 to DAG). REFERENCES 1. ↵ Ezcurra , M. , et al. , Food sensitizes C. elegans avoidance behaviours through acute dopamine signalling . EMBO J , 2011 . 30 ( 6 ): p. 1110 – 1122 . OpenUrl Abstract / FREE Full Text 2. Ryu , L. , et al. , Feeding state regulates pheromone-mediated avoidance behavior via the insulin signaling pathway in Caenorhabditis elegans . Embo j , 2018 . 37 ( 15 ). 3. Burrell , B.D ., Comparative biology of pain: What invertebrates can tell us about how nociception works . J Neurophysiol , 2017 . 117 ( 4 ): p. 1461 – 1473 . OpenUrl CrossRef PubMed 4. ↵ Byrne Rodgers , J. and W.S. Ryu , Targeted thermal stimulation and high-content phenotyping reveal that the C. elegans escape response integrates current behavioral state and past experience . PLOS ONE , 2020 . 15 ( 3 ): p. e0229399 . OpenUrl CrossRef PubMed 5. ↵ Liu , S. , E. Schulze , and R. Baumeister , Temperature- and Touch-Sensitive Neurons Couple CNG and TRPV Channel Activities to Control Heat Avoidance in Caenorhabditis elegans . PLoS One , 2012 . 7 ( 3 ): p. e32360 . OpenUrl CrossRef PubMed 6. ↵ Jordan , A. and D.A. Glauser , Distinct clusters of human pain gene orthologs in Caenorhabditis elegans regulate thermo-nociceptive sensitivity and plasticity . Genetics , 2023 . 224 ( 1 ). 7. Rudgalvyte , M. , et al. , Antagonist actions of CMK-1/CaMKI and TAX-6/calcineurin along the C. elegans thermal avoidance circuit orchestrate adaptation of nociceptive response to repeated stimuli . Elife , 2025 . 14 . 8. Glauser , D.A. , et al. , Heat avoidance is regulated by transient receptor potential (TRP) channels and a neuropeptide signaling pathway in Caenorhabditis elegans . Genetics , 2011 . 188 ( 1 ): p. 91 – 103 . OpenUrl Abstract / FREE Full Text 9. ↵ Schild , L.C. , et al. , The balance between cytoplasmic and nuclear CaM kinase-1 signaling controls the operating range of noxious heat avoidance . Neuron , 2014 . 84 ( 5 ): p. 983 – 96 . OpenUrl CrossRef PubMed 10. ↵ Wittenburg , N. and R. Baumeister , Thermal avoidance in Caenorhabditis elegans: an approach to the study of nociception . Proc Natl Acad Sci U S A , 1999 . 96 ( 18 ): p. 10477 – 82 . OpenUrl Abstract / FREE Full Text 11. ↵ Mohammadi , A. , et al. , Behavioral response of Caenorhabditis elegans to localized thermal stimuli . BMC Neurosci , 2013 . 14 ( 1 ): p. 66 . OpenUrl CrossRef PubMed 12. ↵ Glauser , D.A. and M.B. Goodman , Molecules empowering animals to sense and respond to temperature in changing environments . Curr Opin Neurobiol , 2016 . 41 : p. 92 – 98 . OpenUrl CrossRef PubMed 13. ↵ Goodman , M.B. and P. Sengupta , The extraordinary AFD thermosensor of C. elegans . Pflugers Arch , 2018 . 470 ( 5 ): p. 839 – 849 . OpenUrl CrossRef PubMed 14. ↵ Saro , G. , et al. , Specific Ion Channels Control Sensory Gain, Sensitivity, and Kinetics in a Tonic Thermonociceptor . Cell Rep , 2020 . 30 ( 2 ): p. 397 – 408 e4. OpenUrl CrossRef PubMed 15. ↵ Thapliyal , S. , I. Beets , and D.A. Glauser , Multisite regulation integrates multimodal context in sensory circuits to control persistent behavioral states in C. elegans . Nat Commun , 2023 . 14 ( 1 ): p. 3052 . OpenUrl CrossRef PubMed 16. ↵ Bargmann , C.I ., Chemosensation in C. elegans . WormBook , 2006 : p. 1 – 29 . 17. Colbert , H.A. and C.I. Bargmann , Odorant-specific adaptation pathways generate olfactory plasticity in C. elegans . Neuron , 1995 . 14 ( 4 ): p. 803 – 12 . OpenUrl CrossRef PubMed Web of Science 18. ↵ Kuhara , A. , et al. , Temperature sensing by an olfactory neuron in a circuit controlling behavior of C. elegans . Science , 2008 . 320 ( 5877 ): p. 803 – 7 . OpenUrl Abstract / FREE Full Text 19. ↵ Zaslaver , A. , et al. , Hierarchical sparse coding in the sensory system of Caenorhabditis elegans . Proc Natl Acad Sci U S A , 2015 . 112 ( 4 ): p. 1185 – 9 . OpenUrl Abstract / FREE Full Text 20. ↵ Biron , D. , et al. , An olfactory neuron responds stochastically to temperature and modulates Caenorhabditis elegans thermotactic behavior . Proc Natl Acad Sci U S A , 2008 . 105 ( 31 ): p. 11002 – 7 . OpenUrl Abstract / FREE Full Text 21. ↵ Kotera , I. , et al. , Pan-neuronal screening in Caenorhabditis elegans reveals asymmetric dynamics of AWC neurons is critical for thermal avoidance behavior . Elife , 2016 . 5 . 22. ↵ Beverly , M. , S. Anbil , and P. Sengupta , Degeneracy and neuromodulation among thermosensory neurons contribute to robust thermosensory behaviors in Caenorhabditis elegans . J Neurosci , 2011 . 31 ( 32 ): p. 11718 – 27 . OpenUrl Abstract / FREE Full Text 23. ↵ Harris , G. , et al. , Dissecting the serotonergic food signal stimulating sensory-mediated aversive behavior in C. elegans . PLoS One , 2011 . 6 ( 7 ): p. e21897 . OpenUrl CrossRef PubMed 24. ↵ Mills , H. , et al. , Monoamines and neuropeptides interact to inhibit aversive behaviour in Caenorhabditis elegans . Embo j , 2012 . 31 ( 3 ): p. 667 – 78 . OpenUrl Abstract / FREE Full Text 25. ↵ Flavell , S.W. , D.M. Raizen , and Y.J. You , Behavioral States . Genetics , 2020 . 216 ( 2 ): p. 315 – 332 . OpenUrl Abstract / FREE Full Text 26. Watteyne , J. , et al. , Neuropeptide signaling network of Caenorhabditis elegans: from structure to behavior . Genetics , 2024 . 228 ( 3 ). 27. ↵ Bhat , U.S. , et al. , Neuropeptides and Behaviors: How Small Peptides Regulate Nervous System Function and Behavioral Outputs . Front Mol Neurosci , 2021 . 14 : p. 786471 . OpenUrl CrossRef PubMed 28. ↵ Ezcurra , M. , et al. , Neuropeptidergic Signaling and Active Feeding State Inhibit Nociception in Caenorhabditis elegans . J Neurosci , 2016 . 36 ( 11 ): p. 3157 – 69 . OpenUrl Abstract / FREE Full Text 29. ↵ Glauser , D.A ., Temperature sensing and context-dependent thermal behavior in nematodes . Current Opinion in Neurobiology , 2022 . 73 : p. 102525 . OpenUrl CrossRef PubMed 30. ↵ Lia , A.S. and D.A. Glauser , A system for the high-throughput analysis of acute thermal avoidance and adaptation in C. elegans . J Biol Methods , 2020 . 7 ( 1 ): p. e129 . OpenUrl 31. ↵ Ippolito , D. , S. Thapliyal , and D.A. Glauser , Ca2+/CaM binding to CaMKI promotes IMA-3 importin binding and nuclear translocation in sensory neurons to control behavioral adaptation . eLife , 2021 . 10 : p. e71443 . OpenUrl CrossRef PubMed 32. ↵ Ghaddar , A. , et al. , Whole-body gene expression atlas of an adult metazoan . Sci Adv , 2023 . 9 ( 25 ): p. eadg0506 . OpenUrl CrossRef PubMed 33. ↵ Taylor , S.R. , et al. , Molecular topography of an entire nervous system . Cell , 2021 . 184 ( 16 ): p. 4329 – 4347 .e23. OpenUrl CrossRef PubMed 34. ↵ Ghosh , R. , et al. , Multiparameter behavioral profiling reveals distinct thermal response regimes in Caenorhabditis elegans . BMC Biol , 2012 . 10 : p. 85 . OpenUrl CrossRef PubMed 35. ↵ Lesch , B.J. , et al. , Transcriptional regulation and stabilization of left-right neuronal identity in C. elegans . Genes Dev , 2009 . 23 ( 3 ): p. 345 – 58 . OpenUrl Abstract / FREE Full Text 36. ↵ Troemel , E.R. , A. Sagasti , and C.I. Bargmann , Lateral signaling mediated by axon contact and calcium entry regulates asymmetric odorant receptor expression in C. elegans . Cell , 1999 . 99 ( 4 ): p. 387 – 98 . OpenUrl CrossRef PubMed Web of Science 37. ↵ Gallagher , T. , et al. , ASI regulates satiety quiescence in C. elegans . J Neurosci , 2013 . 33 ( 23 ): p. 9716 – 24 . OpenUrl Abstract / FREE Full Text 38. ↵ Chen , Y. and L.R. Baugh , Ins-4 and daf-28 function redundantly to regulate C. elegans L1 arrest . Developmental Biology , 2014 . 394 ( 2 ): p. 314 – 326 . OpenUrl CrossRef PubMed 39. ↵ Takeishi , A. , et al. , Feeding state functionally reconfigures a sensory circuit to drive thermosensory behavioral plasticity . Elife , 2020 . 9 . 40. ↵ Kimura , K.D. , et al. , The C. elegans Thermosensory Neuron AFD Responds to Warming . Current Biology , 2004 . 14 ( 14 ): p. 1291 – 1295 . OpenUrl CrossRef PubMed Web of Science 41. ↵ Chatzigeorgiou , M. and William R. Schafer , Lateral Facilitation between Primary Mechanosensory Neurons Controls Nose Touch Perception in C. elegans . Neuron , 2011 . 70 ( 2 ): p. 299 – 309 . OpenUrl CrossRef PubMed 42. ↵ Yeon , J. , A. Takeishi , and P. Sengupta , Chronic vs acute manipulations reveal degeneracy in a thermosensory neuron network . MicroPubl Biol , 2021 . 2021 . 43. ↵ Makino , M. , et al. , Regulation of Satiety Quiescence by Neuropeptide Signaling in Caenorhabditis elegans . Front Neurosci , 2021 . 15 : p. 678590 . OpenUrl CrossRef PubMed 44. ↵ Li , W. , S.G. Kennedy , and G. Ruvkun , daf-28 encodes a C. elegans insulin superfamily member that is regulated by environmental cues and acts in the DAF-2 signaling pathway . Genes Dev , 2003 . 17 ( 7 ): p. 844 – 58 . OpenUrl Abstract / FREE Full Text 45. ↵ Park , J.Y. , et al. , A novel functional cross-interaction between opioid and pheromone signaling may be involved in stress avoidance in Caenorhabditis elegans . Sci Rep , 2020 . 10 ( 1 ): p. 7524 . OpenUrl PubMed 46. ↵ Chen , L. , et al. , CKR-1 orchestrates two motor states from a single motoneuron in C. elegans . iScience , 2024 . 27 ( 4 ): p. 109390 . OpenUrl PubMed 47. ↵ Hapiak , V. , et al. , Neuropeptides amplify and focus the monoaminergic inhibition of nociception in Caenorhabditis elegans . J Neurosci , 2013 . 33 ( 35 ): p. 14107 – 16 . OpenUrl Abstract / FREE Full Text 48. ↵ Glauser , D.A ., How and why Caenorhabditis elegans uses distinct escape and avoidance regimes to minimize exposure to noxious heat . Worm , 2013 . 2 ( 4 ): p. e27285 . OpenUrl CrossRef PubMed 49. ↵ Schild , L.C. and D.A. Glauser , Dynamic switching between escape and avoidance regimes reduces Caenorhabditis elegans exposure to noxious heat . Nat Commun , 2013 . 4 . 50. ↵ Lee , Y.-F. , Y.-M. Kuo , and W.-C. Chu , Energy state affects exploratory behavior of tree sparrows in a group context under differential food-patch distributions . Frontiers in Zoology , 2016 . 13 ( 1 ): p. 48 . OpenUrl PubMed 51. ↵ Grunwald Kadow , I.C. , State-dependent plasticity of innate behavior in fruit flies . Current Opinion in Neurobiology , 2019 . 54 : p. 60 – 65 . OpenUrl CrossRef PubMed 52. ↵ Evans , T.C. , (ed), Transformation and microinjection. WormBook , 2006 . 53. ↵ Swierczek , N.A. , et al. , High-throughput behavioral analysis in C. elegans . Nat Methods , 2011 . 8 ( 7 ): p. 592 – 8 . OpenUrl CrossRef PubMed Web of Science View the discussion thread. Back to top Previous Next Posted July 21, 2025. 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Glauser bioRxiv 2025.07.17.665269; doi: https://doi.org/10.1101/2025.07.17.665269 Share This Article: Copy Citation Tools Starvation transforms signal encoding in C. elegans thermoresponsive neurons and suppresses heat avoidance via bidirectional glutamatergic and peptidergic signaling Saurabh Thapliyal , Dominique A. Glauser bioRxiv 2025.07.17.665269; doi: https://doi.org/10.1101/2025.07.17.665269 Citation Manager Formats BibTeX Bookends EasyBib EndNote (tagged) EndNote 8 (xml) Medlars Mendeley Papers RefWorks Tagged Ref Manager RIS Zotero Tweet Widget Facebook Like Google Plus One Subject Area Neuroscience Subject Areas All Articles Animal Behavior and Cognition (7633) Biochemistry (17680) Bioengineering (13889) Bioinformatics (41927) Biophysics (21445) Cancer Biology (18585) Cell Biology (25491) Clinical Trials (138) Developmental Biology (13373) Ecology (19897) Epidemiology (2067) Evolutionary Biology (24308) Genetics (15606) Genomics (22494) Immunology (17736) Microbiology (40385) Molecular Biology (17175) Neuroscience (88583) Paleontology (666) Pathology (2830) Pharmacology and Toxicology (4822) Physiology (7641) Plant Biology (15149) Scientific Communication and Education (2045) Synthetic Biology (4293) Systems Biology (9822) Zoology (2271)