Win-paired cues modulate the effect of dopamine neuron sensitization on decision making and cocaine self-administration: divergent effects across sex

Psychostimulant use and engagement with probabilistic schedules of reward both sensitize the mesocorticolimbic dopamine system. Such behaviours may act synergistically to explain the high comorbidity between stimulant use and gambling disorder. The salient audiovisual stimuli of modern electronic gambling may exacerbate the situation. To probe these interactions, we sensitized ventral tegmental area (VTA) dopamine neurons via chronic chemogenetic stimulation while rats learned the rat gambling task in the presence or absence of casino-like cues. The same rats then learned to self-administer cocaine. In a separate cohort, we confirmed that our chemogenetic methods sensitized the locomotor response to cocaine, and potentiated phasic excitability of VTA dopamine neurons through in vivo electrophysiological recordings. In the absence of cues, sensitization promoted risk-taking in both sexes. When rewards were cued, sensitization expedited the development of a risk-preferring phenotype in males, while attenuating cue-induced risk-taking in females. While these results provide further confirmation that VTA dopamine neurons critically modulate risky decision making, they also reveal stark sex differences in the decisional impact which dopaminergic signals exert when winning outcomes are cued. As previously observed, risky decision-making on the cued rGT increased as both males and females learned to self-administer cocaine. The combination of dopamine sensitization and win-paired cues while gambling lead to significantly greater cocaine-taking, but these rats did not show any increase in risky choice as a result. Cocaine and heavily-cued gambles may therefore partially substitute for each other once the dopamine system is rendered labile through sensitization, compounding addiction risk across modalities.