Synaptogyrin-3 promotes behavioral resilience and protects against cocaine-induced dopaminergic adaptations

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PROJECT SUMMARY Synatptogyrin-3 (SYG3) is a cocaine-sensitive synaptic vesicle protein that is yet to be fully characterized in the context of cocaine use disorder. SYG3 is highly expressed in dopamine-containing neurons and directly interacts with the dopamine transporter (DAT), suggesting a role in synaptic dopamine dynamics. Preliminary studies from our laboratory suggest that cocaine breakpoint on a progressive ratio schedule of reinforcement, a behavioral proxy for “motivation”, negatively correlates with mesolimbic SYG and DAT levels in cocaine self- administering rats. Moreover, I found that overexpression of SYG3 in VTA dopamine neurons decreases anxiety-like behavior and alters dopamine system function. Therefore, the objective of this proposal is to examine the relationship between SYG3, the DAT, and cocaine self-administration. My overarching hypothesis is that high innate levels of SYG3 induce a resilient behavioral phenotype and prevent cocaine-induced dopamine dysfunction. I will peruse this hypothesis by answering the following 3 specific questions: (1) What drives the inverse relationship between cocaine breakpoint and SYG3 levels? (2) Will overexpression of SYG3 in VTA dopamine neurons reduce cocaine self-administration behaviors? (3) Will overexpression of SYG3 in VTA dopamine neurons protect against cocaine-induced dopamine dysfunction? We will pursue these aims using both behavioral and neurochemical techniques, including affective behavioral tests, cocaine self- administration, viral manipulations, as well as molecular and neurochemical analyses—all to determine if SYG3 influences cocaine-taking behavior and cocaine-induced dopamine dysfunction. The proposed research is significant, since there is no FDA approved pharmacotherapy for cocaine use disorder. The results from this proposal will further characterize the relatively unknown synaptic vesicle protein, SYG3, as a fruitful cellular target for pharmacotherapeutics to treat cocaine use disorder.