Dopamine circuit regulation of morphine reinforcement across the opioid exposure cycle

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PROJECT SUMMARY Pathological adaptions in the ventral tegmental area (VTA) dopamine system associated with chronic exposure to opioids and opioid withdrawal can dysregulate responsivity to opioids and contextual cue associations. The primary goal of this training proposal is to gain new skills in advanced computational techniques to delineate how functionally diverse subpopulations of VTA dopamine neurons are regulated during morphine exposure and the formation of morphine contextual associations in non-dependent and morphine-dependent mice. Foundational findings have identified the intrinsic and synaptic (glutamatergic and GABAergic) adaptations that VTA dopamine neurons undergo throughout acute and chronic opioid exposure. Yet, few studies have accounted for the functional diversity of VTA dopamine neurons that mediate distinct aspects of cue-reward processing and motivation. Dissociating the potential diversity of VTA dopamine responses in the development of opioid dependence will help unravel the neural basis of the progression of opioid-use disorder. The Zweifel lab has previously used a genetic approach to isolate functionally distinct subpopulations of dopamine neurons that project to discrete regions of the nucleus accumbens (NAc). Corticotrophin releasing hormone receptor 1 (Crhr1)-Cre VTA dopamine neurons were found to selectively project to the NAc Core (VTACore) and cholecystokinin (Cck)-Cre VTA dopamine neurons selectively project to the NAc medial Shell (VTAmShell). I hypothesize that there exist projection-specific neural and behavioral correlates in response to morphine and during the formation of morphine contextual associations in non-dependent and morphine-dependent mice. I will investigate this using a systematic approach across three aims. For Aim 1 (K99), I will use behavioral pharmacology and fiber photometry to determine whether VTACore and VTAmShell dopamine neurons engage in uniform or differential dose-dependent neural activation dynamics in non-dependent and morphine dependent mice. For Aim 2 (K99), I will use my skills in conditioned place preference and in vivo fiber photometry to determine how the VTACore and VTAmShell neurons encode contextual associations to morphine in non-dependent and morphine dependent mice. For Aim 3 (R00), I will determine the basis of these pathological adaptations in VTA dopamine subpopulations by dissecting the role mu-opioid receptor (MOR)- sensitive GABAergic inputs play in morphine contextual associations. During the K99 mentored phase, I will gain new scientific training in Dr. Larry Zweifel’s laboratory, augmented by my advisory committee, in computational analytical tools to analyze complex neurophysiological and behavioral data sets. I will also gain new career development training from Dr. Zweifel, my advisory committee, and the MOSAIC UE5 program that will facilitate my transition into a successful independent principal investigator in academia. Importantly, I will continue my work on increasing representation and equity in the biomedical research workforce.