IBUPROFEN OR PREGABALIN REDUCE THE HUMAN SPINAL CORD NEUROVASCULAR COUPLING RECORDED BY FUNCTIONAL NEAR-INFRARED SPECTROSCOPY

IBUPROFEN OR PREGABALIN REDUCE THE HUMAN SPINAL CORD NEUROVASCULAR COUPLING RECORDED BY FUNCTIONAL NEAR-INFRARED SPECTROSCOPY | Authorea try { document.documentElement.classList.add('js'); } catch (e) { } var _gaq = _gaq || []; _gaq.push(['_setAccount', 'G-8VDV14Y67G']); _gaq.push(['_trackPageview']); (function() { var ga = document.createElement('script'); ga.type = 'text/javascript'; ga.async = true; ga.src = ('https:' == document.location.protocol ? 'https://ssl' : 'http://www') + '.google-analytics.com/ga.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(ga, s); })(); Skip to main content Preprints Collections Wiley Open Research IET Open Research Ecological Society of Japan All Collections About About Authorea FAQs Contact Us Quick Search anywhere Search for preprint articles, keywords, etc. Search Search ADVANCED SEARCH SCROLL This is a preprint and has not been peer reviewed. Data may be preliminary. 15 April 2025 V1 Latest version Share on IBUPROFEN OR PREGABALIN REDUCE THE HUMAN SPINAL CORD NEUROVASCULAR COUPLING RECORDED BY FUNCTIONAL NEAR-INFRARED SPECTROSCOPY Authors : Sergio Uribe , Juan Oyarzún , Raul Caulier-Cisterna , and Antonio Eblen-Zajjur 0000-0002-0077-0318 [email protected] Authors Info & Affiliations https://doi.org/10.22541/au.174471864.49011834/v1 410 views 158 downloads Contents Abstract Information & Authors Metrics & Citations View Options References Figures Tables Media Share Abstract Background and Purpose: Brain neurovascular coupling (NVC) involves voltage-gated Ca++ channels (VGCC) and prostaglandins. However, their differential contribution in the spinal cord neurovascular coupling (NVC) is unknown. This study used non-invasive functional near infrared spectroscopy (fNIRS) to assess how ibuprofen (COX inhibitor) and pregabalin (VGCC α2δ subunit binder) affect human perispinal neurovascular responses (NVR). Experimental Aproach: Perispinal cervical and lumbar NVRs elicited by painless electrical stimulation of the posterior tibial nerve were recorded using a non-invasive fNIRS technique before and 60 minutes after oral administration of a single clinical dose of 10mg∙kg-1 IBU (n=38) or 75 mg PGL (n=32) in healthy volunteers. Key Results: IBU reduced the NVR amplitude by 17% (Lumbar) and 34% (Cervical), rise time by 20% (Lumbar) and 25% (Cervical), and duration by 12% (Lumbar) and 20% (Cervical). PGL reduces the amplitude of perispinal NVR by 35% (Lumbar) and 70% (Cervical) and its duration by 20% (Lumbar) and 30% (Cervical). Conclusion and Implications: These results demonstrate the differential pharmacological intensity effect of clinical dose of IBU or PGL across cervical and lumbar spinal cord levels, but also contribution of the neuronal excitability, mediated by Ca++ channels, and prostaglandins in the perispinal NVR. Furthermore, they underscore the potential of the fNIRS for monitoring the pharmacological effects of IBU and PGL on the human spinal cord. IBUPROFEN OR PREGABALIN REDUCE THE HUMAN SPINAL CORD NEUROVASCULAR COUPLING RECORDED BY FUNCTIONAL NEAR-INFRARED SPECTROSCOPY Sergio Uribe 1 ǀ Juan-Esteban Oyarzún 2 ǀ Raúl Caulier-Cisterna 3 ǀ Antonio Eblen-Zajjur 4,* 1 Department of Medical Imaging and Radiation Sciences, School of Primary and Allied Health Care, Faculty of Medicine, Nursing and Health Sciences, Chancellors Walk, Clayton Campus, Victoria, Australia. 2 Center for Biomedical Imaging, the Radiology Department, School of Medicine, Pontificia Universidad Católica de Chile, Santiago, Chile. 3 Department of Informatics and Computing, Faculty of Engineering, Universidad Tecnológica Metropolitana, Santiago, Chile. 4 Translational Neuroscience Laboratory, Instituto de Ciencias Biomédicas, Facultad de Ciencias de la Salud, Universidad Autónoma de Chile, Santiago, Chile. *Corresponding Author: [email protected] Cel. +56 9 44292800 ABSTRACT Background and Purpose: Brain neurovascular coupling (NVC) involves voltage-gated Ca ++ channels (VGCC) and prostaglandins. However, their differential contribution in the spinal cord neurovascular coupling (NVC) is unknown. This study used non-invasive functional near infrared spectroscopy (fNIRS) to assess how ibuprofen (COX inhibitor) and pregabalin (VGCC α2δ subunit binder) affect human perispinal neurovascular responses (NVR). Experimental Aproach: Perispinal cervical and lumbar NVRs elicited by painless electrical stimulation of the posterior tibial nerve were recorded using a non-invasive fNIRS technique before and 60 minutes after oral administration of a single clinical dose of 10mg∙kg -1 IBU (n=38) or 75 mg PGL (n=32) in healthy volunteers. Key Results: IBU reduced the NVR amplitude by 17% (Lumbar) and 34% (Cervical), rise time by 20% (Lumbar) and 25% (Cervical), and duration by 12% (Lumbar) and 20% (Cervical). PGL reduces the amplitude of perispinal NVR by 35% (Lumbar) and 70% (Cervical) and its duration by 20% (Lumbar) and 30% (Cervical). Conclusion and Implications: These results demonstrate the differential pharmacological intensity effect of clinical dose of IBU or PGL across cervical and lumbar spinal cord levels, but also contribution of the neuronal excitability, mediated by Ca ++ channels, and prostaglandins in the perispinal NVR. Furthermore, they underscore the potential of the fNIRS for monitoring the pharmacological effects of IBU and PGL on the human spinal cord. Keywords: Ibuprofen, Pregabalin, Human Spinal Cord, Neurovascular Coupling, Prostaglandins, Calcium Channels, non-invasive fNIRS. 1 ǀ INTRODUCTION Neurovascular coupling (NVC), the dynamic coordination between neural activity and localized blood flow regulation, ensures metabolic demands are met during neuronal activation (Chen et al., 2014; Filosa et al., 2016a; Tarantini et al., 2016a; Stackhouse and Mishra, 2021a; Yang et al., 2024). While extensively characterized in the brain, spinal NVC mechanisms remain understudied despite emerging parallels in signaling pathways involving neurons, astrocytes, vascular smooth muscle, and endothelial cell (Aasted et al., 2016; Kussman et al., 2016; Peng et al., 2018; Stackhouse and Mishra, 2021b; Valenzuela et al., 2021; Ayaz et al., 2022; Oyarzún et al., 2022; Yang et al., 2024). These cells communicate via membrane receptors (e.g., EP2, NMDA), ion channels (Ca²⁺, TRPC1/V4), and mediators like glutamate, nitric oxide (NO), CO₂, adenosine, lactate, K⁺, prostaglandin (PGE₂) (Phillips et al., 2016; Stackhouse and Mishra, 2021a; Yang et al., 2024), enzymes (PLA₂, COXs, FRAP, ATPase, eNOS), myoendothelial gap junctions, connexins (CX 47 ), and integrins (Vanegas and Schaible, 2001; Vasquez et al., 2001; Glykys et al., 2003; Czaplinski et al., 2005; De Wit and Griffith, 2010; Bosco-Bruno et al., 2012; Filosa and Iddings, 2013; Filosa et al., 2016b; Tarantini et al., 2016b, 2017; Watanabe et al., 2018; Bahr-Hosseini and Bikson, 2021). Astrocyte-derived PGE₂ acts on EP 2 /EP 4 receptors in vascular smooth muscle and endothelial cells, inducing relaxation and vasodilation (Vanegas and Schaible, 2001). however, differential contributions of each of these biochemical pathways to the NVR is poorly known. Astrocytes amplify PGE₂ synthesis, which activates vascular EP2/EP4 receptors to induce vasodilation—a process critical in both health and cerebrovascular disorders such as stroke and dementia (Phillips et al., 2016; Squair et al., 2020; Stackhouse and Mishra, 2021a; Yang et al., 2024). The clinical relevance of NVC lies in its dual role as a diagnostic biomarker and therapeutic-monitor target. Dysregulated NVC precedes structural damage in conditions like cerebral small vessel disease and vascular cognitive impairment, offering a window for early intervention (Squair et al., 2020; Stackhouse and Mishra, 2021a; Yang et al., 2024). Pharmacological modulation of NVC components—including cyclooxygenase (COX) inhibitors like ibuprofen (IBU) (Jang et al., 2020) and voltage-gated calcium channel ligands like pregabalin (PGL)—demonstrates translational potential. IBU attenuates cortical hyperemic responses by suppressing PGE₂-driven vasodilation, while PGL binds to α2δ subunits of VGCC, reducing Ca²⁺ influx and neurotransmitter release (Mathieson et al., 2020) and neuronal excitability, additionally, it attenuates blood oxygen level-dependent (BOLD) responses in the visual cortex and cerebral blood flow in the prefrontal cortex (Aupperle et al., 2012) (Phillips et al., 2016; Squair et al., 2020; Stackhouse and Mishra, 2021a) (Naulaers, 2005; Szabo et al., 2014; Hodkinson et al., 2015a; Le et al., 2018). However, their impact on spinal NVC remains unexplored, however, some evidence suggests that analogous pathways exist in spinal regions (Aasted et al., 2016; Kussman et al., 2016; Peng et al., 2018; Valenzuela et al., 2021; Ayaz et al., 2022; Oyarzún et al., 2022). Here, functional near-infrared spectroscopy (fNIRS), a validated tool for assessing NVC dynamics (Phillips et al., 2016; Squair et al., 2020; Stackhouse and Mishra, 2021a; Oyarzún et al., 2022; Appelgren et al., 2023; Caulier-Cisterna et al., 2024) was applied to evaluate IBU and PGL’s effects on perispinal hemodynamics in humans. Elucidating these drug effects could monitor the therapeutic response at the spinal cord where NVC dysregulation contributes to pathology but now remains under addressed. 2 ǀ METHODS The study involved healthy volunteers of any sex, randomly assigned to the IBU or PGL groups, recruited from the university community. Inclusion criteria were any gender, age between 18 to 65 years, no morbidity, no pharmacological treatment, no allergy to either IBU or PGL, no history of gastrointestinal susceptibility neither to IBU nor to PGL, body mass index (BMI) below 30, and being asymptomatic. Subjects with drug or alcohol abuse, spinal trauma, or those taking any NSAID less than 48 hours before the fNIRS test, were excluded from the study. Experimental protocols were approved by the institutional ethics committee (PUC-170914003). All subjects were included in the study after their written informed consent. 2.1 ǀ Peri-spinal fNIRS recording The experimental setup was detailed and described elsewhere (Valenzuela et al., 2021; Oyarzún et al., 2022; Appelgren et al., 2023; Caulier-Cisterna et al., 2024). Briefly, peri-spinal NVR was triggered by non-invasive electrical stimulation of the left tibialis posterior nerve, using an electrical stimulator (WPI TM A350) and a bipolar surface electrode (square pulses, 10 mA, 5 ms, proximal cathode, 3 cm separated to the anode) applied on the skin in the ventral midline of the left wrist. Two arrays of two infrared light emitters and two detectors operating at 750 nm and 850 nm for a total of 8 HbO 2 and Hb concentration recording channels, were placed at cervical and lumbar levels. The emitter-detector optode distance was 4.5 cm to achieve a recording depth of 1.5 to 2 cm. These optodes were placed on the skin of the volunteer’s back, with the vertebral spinous processes serving as anatomical landmarks at the cervical (C7 and T1) and lumbar (T8 and T10) levels, which are near the cervical and lumbar spinal cord sensory enlargements, respectively (Figure 1). 2.2 ǀ Experimental protocol Healthy volunteers were randomly assigned to the IBU or PGL group. In a quiet and dimly light clinical room, they were informed about the test, then instructed to lie down in a prone position on a massage bed with the face inside the face cradle of the bed. The flexible optode holders were placed as shown in Fig. 1 using clinical non-allergic adhesive. A black blanket was used to cover the volunteer´s back to avoid any light contamination during the recordings. Recording of the peri-spinal NVR during basal conditions was performed following the stimulation and recording protocol described below. Thereafter, volunteers were asked to sit down, and were disconnected from the stimulator and fNIRS device while maintaining all optodes and electrodes in place. Subsequently, a single clinical dose of IBU 10 mg∙Kg -1 (Lab. Chile ® , dissolved in 100 mL water) or 75 mg PGL (Abbott ® , dissolved in 100 mL water) was given to volunteers orally. Sixty minutes after drug administration, the recording of the peri-spinal NVR was repeated using the same protocol as for the basal recording. The re-test time was selected because oral administration of IBU or PGL result in maximum plasma concentrations within 1 hour (Canaparo et al., 2000; Bockbrader et al., 2010). FIGURE 1 Left: Non-invasive bipolar electrode for left tibial posterior electrical stimulation at the left ankle, with cathode (red) proximal. Right: Location of the surface optodes at the volunteers’ back, red circles (vertical aligned) are laser light emitters and green circles (horizontal aligned) are optical detectors at cervical (C7) and lower thoracic (T10) vertebral levels, for a total of 8 fNIRS recording channels. 2.3 ǀ Stimulation and Recording Protocol A bipolar electrode was non-invasively placed at the left tibialis posterior nerve at the medial malleolus-Achillean channel. The recording protocol consisted of applying three electrical stimuli with an intensity of 10 mA at 4-minute intervals. This pattern was selected to prevent spinal dorsal horn phenomena such as potentiation, sensitization or short or long-term depression (Chen et al., 2014; Filosa et al., 2016a; Tarantini et al., 2016a; Stackhouse and Mishra, 2021a; Yang et al., 2024). At the end of the protocol, volunteers from both groups were asked to indicate the subjective pain intensity produced by the stimulation during the recording, using the visual analog scale (VAS)(Heller et al., 2016). 2.4 ǀ Nerve conduction velocity (NCV) The NCV of the left tibialis posterior nerve was recorded (Surpass Workstation ® , v4.4.6, EMS Biomedical, Germany) to exclude alterations in spinal NVR induced by peripheral nerve disease, based on abnormal NCV according to clinical values (Kimura, 2001; Kim et al., 2022). 2.5 ǀ Measurements and Statistical Methods The fNIRS device used in the present study (Oxymon™; Artinis Medical System) measured both HbO 2 and Hb concentrations (mmol∙L -1 ) using the Modified Beer-Lambert Law (MBLL) (Valenzuela et al., 2021; Appelgren et al., 2023; Caulier-Cisterna et al., 2024), however, the HbO 2 signal was approximately one order of magnitude higher than that of the Hb. Therefore, the analysis focused on the HbO 2 signal and neuronal activity-related oxygenation (Valenzuela et al., 2021; Appelgren et al., 2023; Caulier-Cisterna et al., 2024). The rise time (RT; time between stimulus application and maximal NVR amplitude in seconds), amplitude (AMP; maximal amplitude of the NVR in optical density units) and duration (width at half-maximum duration of the NVR (FWHM) in seconds of the peri-spinal NVR were measured and processed using non-parametric statistics. The median and 25-75 percentiles were calculated from three consecutive spinal NVRs. Bland-Altman plots were also evaluated to show the potential proportional bias between baseline and post-drug measurements. The NVR values were compared between the groups but among the cervical and thoracic recording locations in each group. Mann-Whitney test (M-W) was used for two-groups comparison while the Kruskal-Wallis test (K-W) was used for multi-group comparisons, p<0.05 was set for significance. 3 ǀ RESULTS 3.1 ǀ Sample characteristics A total of 38 volunteers in the IBU group and 32 in the PGL group were evaluated. The clinical characteristics are presented in detail in the Table 1. No statistical differences were found between the volunteers in both groups. 3.2 ǀ Peri-spinal NVR changes induced by ibuprofen Sixty minutes after a single oral dose of IBU, a statistically significant decrease (-45 %; p<0.05) in cervical NVR amplitude was detected compared to basal values and a decrease in the cervical rise time (-15.5 %; p<0.05) but not at the lumbar level (Figs. 2, 3A, 3B, 3D, 3G, 3E and 3H) was observed. However, 78.4% of the volunteers in this group showed lower lumbar NVR amplitudes (p<0.05) after IBU (Table 2; Figs. 3A, 3D and 3G). The NVR duration (FWHM) was reduced by IBU at both cervical (-24.8%) and lumbar (-17.5%) sites (p<0.05; Figs. 2, 3C, 3F and 3I). 3.3 ǀ Peri-spinal NVR changes induced by pregabalin A single dose of PGL reduced the mean cervical NVR amplitude in 72.2% (Fig. 4). While the mean lumbar NVR amplitude was not statistically different from the basal values, 76% of the volunteers showed a reduction of this parameter after PGL (p<0.01; Fig. 5A, 5D and 5G). No significant difference in rise time was detected after PGL (Figs. 4 and 5B, 5E and 5H). The duration of NVR at both the cervical and lumbar levels was reduced by -14.5% and -18.8%, respectively (Figs. 4 and 5C, 5F and 5I). TABLE 1 Clinical characteristics of healthy volunteers from ibuprofen (IBU) and pregabalin (PGL) groups GROUPS Parameter IBU PGL n 38 32 Gender: F; % 39% 50% Age (years) 28 ± 9 29 ± 10 Height (cm) 169 ± 9 167 ± 10 Weight (Kg) 68 ± 10 65 ± 10 BMI (Kg·m -1 ) 23 ± 2 23 ± 2 Single Oral Dose 10 mg∙Kg -1 75 mgF: Female, BMI: Body mass index, n is the total volunteer’s group. No statistical differences were found between groups. Values are mean ± SD. 3.4 ǀ Peri-spinal NVR changes induced by ibuprofen or pregabalin The percentage of volunteers with changes in perispinal NVR parameters after administration of clinical doses of IBU or PGL is presented in Table 2 and Fig. 6. These show that IBU reduced the cervical NVR rise time, amplitude and duration in more than 70 % of the volunteers (p<0.05) and that PGL also reduces the perispinal NVR amplitude in more than 70 % of the volunteers (p<0.05). FIGURE 2 Effects of a single dose of IBU on the peri-spinal NVR elicited by electrical stimulation of the left tibialis posterior nerve recorded at the cervical (upper panels) and lumbar (lower panels) spinal levels. The colored lines represent the median value from volunteers 60 minutes after oral administration of IBU (10 mg∙kg -1 ). Gray areas indicate the 25th-75th percentiles of control NVR (before IBU). FIGURE 3 Effects on perispinal NVR before and after a single oral dose of IBU (10 mg∙kg -1 ) in 38 healthy subjects. A: Median and 25th-75th percentile of amplitude; B: rise time and; C: duration; D to I: Bland Altman plots of percentage of differences between control and post ibuprofen measurement at cervical (D to F) or lumbar level (G to I). The Mann-Whitney U statistical test was performed for intra and intergroup comparisons. Asterisks (*) represent statistically significant differences (p<0.05). A single proportion test was used for the percentage of volunteers with NVR changes. TABLE 2 Percentage of volunteers with perispinal NVR parameters changes after administration of clinical doses of IBU or PGL GROUPS NVR Parameter IBU PGL Rise Time (s) Cervical (-) 72.2%** (-) 44.8% n.s. Lumbar (-) 56.8% n.s. (-) 55.6% n.s. Amplitude (mmol∙L -1 ) Cervical (-) 78.4%*** (-) 75.0%** Lumbar (-) 70.3%** (-) 76.0%** Duration (s) Cervical (-) 74.4%** (-) 62.1% n.s. Lumbar (-) 73.0%** (-) 63.0% n.s. (-) reduction effect; % of volunteers with the effect; *p<0.05; **p<0.01; ***<0.001; n.s. no significant. Single proportion test was used for the percentage of volunteers with NVR changes. FIGURE 4 Effects of a single dose of PGL on the peri-spinal NVR elicited by electrical stimulation of the left tibialis posterior nerve, recorded at cervical (upper panels) and lumbar (bottom panels) spinal levels. Colored lines represent the median value from volunteers 60 minutes after an oral administration of PGL (75 mg). Gray areas indicate the 25th-75th percentiles of control NVR (before PGL). Percentage of NVR amplitude reduction post pregabalin is presented for cervical and lumbar recording sites. FIGURE 5 Effects on perispinal NVR before and after a single oral dose of PGL (75 mg) on perispinal NVRs in 32 healthy subjects. A: Median and 25th-75th percentile of amplitude; B: rise time and; C: duration; D to I: Bland Altman plots of percentage of differences between baseline and post-ibuprofen measurement at cervical (D to F) or lumbar level (G to I). The Mann-Whitney statistical test was performed for intra- or intergroup comparisons. Asterisks (*) represent statistically significant differences (p<0.05). 4 ǀ DISCUSSION AND CONCLUSIONS The present study reports for the first time the effects of clinical doses of ibuprofen- or pregabalin on changes in the cervical and lumbar perispinal neurovascular responses triggered by peripheral electrical stimulation of the tibialis posterior nerve in healthy volunteers. Both drugs were able to alter the amplitude, rise time, and/or the duration of the perispinal NVR at the cervical and/or lumbar levels, defining differential contributions of each of these biochemical pathways to the perispinal NVR. FIGURE 6 Reduction on perispinal NVR after a single clinical oral dose of IBU (10 mg∙kg -1 ) or PGL (75 mg) on perispinal NVRS in 38 or 32 healthy subjects respectively, expressed as percentage of volunteers with reduced perispinal NVR parameters, i.e., amplitude (Amp, red); rise time (RT, green) and duration (Dur, blue), recorded at Cervical (C) or Lumbar (L) spinal locations. The percentage of volunteers with the reducing effect on NVR parameters Percentages were tested the single proportion test; *p<0.05; **p<0.01; ***<0.001; n.s. no significant difference. 4.1 ǀ Effects of ibuprofen on spinal blood flow There are no Ibuprofen specific effects that have been previously reported for spinal blood flow. However, the effect on cerebral blood flow (CBF) appears to vary depending on the context and population studied. In a report involving healthy participants, ibuprofen did not affect regional cerebral blood flow under pain-free conditions. However, it did show increased activation of certain brain circuits in a postsurgical state, suggesting a role in modulating pain rather than altering baseline CBF directly (Hodkinson et al., 2015a). Some reports suggest that while indomethacin significantly reduces CBF and cerebral oxygen delivery, ibuprofen has a lesser impact (Naulaers, 2005; Stark et al., 2022). The fNIRS measurement of the cerebral circulation in preterm babies treated with ibuprofen, did not show significant changes in cerebral blood volume or flow compared to placebo (Naulaers, 2005), suggesting that ibuprofen’s influence on CBF may be minimal in these patients. It has been proposed that ibuprofen might improve CBF following global cerebral ischemia, highlighting its potential neuroprotective effects under specific pathological conditions (Grice et al., 1987; Iwata et al., 2010), however, ibuprofen does not appear to alter the physiological CO 2 -induced vasodilation and fundamental regulatory mechanisms of cerebral blood flow (Pellicer et al., 1999). Another NSAID, indomethacin is known to decrease CBF by 18-30%, particularly noticeable about 60 minutes after administration. This effect can lead to central nervous system (CNS) side effects, which may correlate with drug levels in sensitive individuals (Seideman and von Arbin, 1991; Jones and Dinsmore, 2002; Stark et al., 2022). Indomethacin’s vasoconstrictive effects are believed to occur through mechanisms beyond just prostaglandin inhibition, although the exact pathways remain unclear (Jones and Dinsmore, 2002). Despite the fact that ibuprofen does not significantly alter regional CBF under pain-free conditions, it may activate certain brain circuits associated with pain modulation without changing the baseline CBF (Naulaers, 2005; Hodkinson et al., 2015a). In studies involving preterm infants, ibuprofen administration showed no significant difference in cerebral blood volume or flow compared to placebo, suggesting a lack of acute impact on cerebral circulation (Naulaers, 2005). In contrast to indomethacin, the Ibuprofen did not affect baseline cerebral circulation or physiological responses to increased CO 2 levels (hypercarbia), indicating that its role in modulating CBF might be limited under normal physiological conditions (Pellicer et al., 1999; Iwata et al., 2010). Diclofenac has been shown not to significantly affect CBF velocity in patients with supratentorial tumors, indicating that it may not exert substantial influence on cerebral hemodynamics (Jones and Dinsmore, 2002). On the other hand, indomethacin decreases cerebral blood flow (CBF) through several mechanisms, primarily involving its action as a non-selective COXs inhibitor, leading to a reduction in the synthesis of prostacyclin (PGI2) and PGE2, thereby promoting vasoconstriction and decreased CBF (Martín-Saborido et al., 2019). Indomethacin has been identified as a potent cerebral arteriolar vasoconstrictor with a significant reduction in CBF, particularly about 60 minutes after administration (Seideman and von Arbin, 1991; Martín-Saborido et al., 2019) with CBF reductions up to 30% (Seideman and von Arbin, 1991). Indomethacin also inhibits phospholipase A 2 , which releases arachidonic acid from membrane phospholipids (Vanegas and Schaible, 2001), decreasing the production of various vasoactive mediators for vasodilation (Vanegas and Schaible, 2001). Studies indicate that ibuprofen does not significantly alter regional cerebral blood flow under pain-free conditions. However, it has been shown to enhance the activation of descending modulatory circuits in the brain following painful stimuli, suggesting a role in altering neurovascular dynamics during pain states (Hodkinson et al., 2015a). Under conditions of pain, ibuprofen appears to facilitate cortical neurovascular coupling by reducing peripheral sensitization and central sensitization. This dual action may lead to improved cerebral blood flow responses in areas associated with pain processing (Hodkinson et al., 2015a). Our results show that in the human spinal cord, the predominant effect of clinical doses of ibuprofen is the reduction of the perispinal NVR, leading to a neurovascular un-coupling. Acute administration of ibuprofen has been linked to temporary reduction of brain aging indicator, probably due to its anti-inflammatory effect by reducing inflammatory mediators (Szabo et al., 2014; Le et al., 2018). In the rat spinal cord, Ibuprofen exerted inhibition of RhoA, which regulated neuronal cytoskeleton and growth signaling enhancing the neurovascular coupling (Dill et al., 2010). This effect did not occur in human recordings of the perispinal NVR, where ibuprofen induced neurovascular un-coupling. 4.2 ǀ Contribution of spinal prostaglandins to the perispinal NVR in humans Chronic simultaneous treatment with the epoxygenase inhibitor MSPPOH, the NO synthase inhibitor L-NAME, and the non-specific COX inhibitor indomethacin in mice decreased the cortical NVR amplitude triggered by electrical sensory stimulation by 55.5% (Tarantini et al., 2017). This percentage of reduction likely reflects the contribution of these three metabolic pathways to the mice cortical NVR. Despite the interspecies differences, this previous report contrasts with our human result where, ibuprofen, a widely used non-specific COXs inhibitor, administered at a clinical single dose, was able to reduce the perispinal NVR amplitude about 45.1%. This strongly support the notion of the main role of prostaglandins in the human perispinal NVR. 4.3 ǀ Effects of pregabalin on spinal blood flow Pregabalin, primarily known for its role in managing neuropathic pain and seizures, may also influence neurovascular coupling through several mechanisms. Pregabalin binds to the α2δ subunit of voltage-gated calcium channels, reducing calcium influx at nerve terminals (Eblen-Zajjur, 2000; Boroujerdi et al., 2011; Gou et al., 2021) and the release of excitatory neurotransmitters like glutamate, norepinephrine, and substance P, potentially dampening neuronal excitability and altering neurovascular responses (Deitos et al., 2018; Onakpoya et al., 2019; Alles et al., 2020). This effect may help stabilize neuronal circuits that are otherwise hyperexcitable, which is particularly relevant in conditions like fibromyalgia where neurovascular coupling may be disrupted due to altered excitatory/inhibitory balance (Deitos et al., 2018; Alles et al., 2020). These changes may suggest an improvement in the balance between excitation and inhibition within cortical networks (Alles et al., 2020); however, our human perispinal NVR recordings under normal conditions showed that the primary pregabalin effect is to reduce the neuronal excitability, thus, reducing the neuronal discharge resulting in a lower release of neuronal and astrocytic vasodilation factors (see introduction). That effect contrast with experimental models of ischemic stroke, where pregabalin was able to promote a post-injury axonal regeneration which might improve neurovascular coupling in damaged brain regions (Kugler et al., 2022). Pregabalin shows acute (few minutes) and long-term (Chronic) effects on neurovascular coupling (Alles et al., 2020; Kugler et al., 2022). The effects reported in the present study corresponds to the acute effect on the perispinal NVR, further research should address the chronic pregabalin effect on the spinal cord NVR. While it has been shown to enhance activation of descending modulatory circuits in the brain during pain states, it does not significantly alter regional cerebral blood flow under pain-free conditions (Szabo et al., 2014; Hodkinson et al., 2015b). Its analgesic effects may lead to improved regulation of cerebral blood flow in response to neuronal activity during painful stimuli. Differential cervical-lumbar effects on perispinal NVRs to IBU or PGL could be explained by the differential metameric distribution of sensory related enzymes and/or enzymatic activities such as fluoride-resistant acid phosphatase (FRAP) (Glykys et al., 2003; Eblen-Zajjur, 2005; Sosa et al., 2013), and adenosine triphosphatase (ATPase) and its variants (Na + /K + -ATPase, H + /K + -ATPase, and Ca 2+ -ATPase) (Czaplinski et al., 2005; Reyes et al., 2009; Eblen-Zajjur et al., 2015). The frequent combined clinical use of IBU and PGL in patients with chronic low back pain could synergistically reduce the neurovascular coupling due to their different mechanisms of action but with their final common pathway i.e., the perispinal NVR. Disclosures This study was funded by FONDEF grant ID21I10092 and Fundación COPEC-UC grant 2018R.1030 (to SU and AE-Z). Fondecyt Postdoctorado 2023-3230777, Fondecyt Iniciación 11250867, Research Assistant Funding UTEM, 2024-AI23-08, Universidad Tecnológica Metropolitana (to RC-C), Ethical approval Experimental protocols have been approved by the ethics committee of the Pontificia Universidad Católica de Chile (PUC-170914003). All subjects were included in the study after their written informed consent. Conflicts of interest Authors declare no conflicts of interest Author contributions A.E-Z and S.U.—Conceptualization; data curation; formal analysis; methodology; project administration; validation; visualization; writing—original draft; writing—review and editing; R.C-C., J.E.O., A.E-Z and S.U.—provided analytical tools and equipment; visualization; J.E.O., R.C-C., and A.E-Z—performed experiments; All authors analyzed data; S.U and A.E-Z—interpreted results of experiments; S.U and A.E-Z drafted, edited and revised the manuscript. 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Keywords analgesics clinical pharmacology neuropharmacology neurophysiology neuroscience pain physiology therapeutic drug monitoring vascular biology Authors Affiliations Sergio Uribe Monash University View all articles by this author Juan Oyarzún Pontificia Universidad Católica de Chile View all articles by this author Raul Caulier-Cisterna Universidad Tecnológica Metropolitana View all articles by this author Antonio Eblen-Zajjur 0000-0002-0077-0318 [email protected] Universidad Autónoma de Chile, Facultad de Ciencias de la Salud View all articles by this author Metrics & Citations Metrics Article Usage 410 views 158 downloads .FvxKWukQNSOunydq8rnd { width: 100px; } Citations Download citation Sergio Uribe, Juan Oyarzún, Raul Caulier-Cisterna, et al. IBUPROFEN OR PREGABALIN REDUCE THE HUMAN SPINAL CORD NEUROVASCULAR COUPLING RECORDED BY FUNCTIONAL NEAR-INFRARED SPECTROSCOPY. Authorea . 15 April 2025. 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