PROJECT SUMMARY Human immunodeficiency virus type 1 (HIV-1) affects over 38 million people worldwide today. While current treatment strategies effectively suppress virus replication in peripheral tissues, the central nervous system remains vulnerable to damage induced by viral proteins, which enter soon after initial infection and are not well targeted by most antiretroviral therapies. It is thus critical to focus efforts on development of supplemental intervention strategies to address persistent inflammation which presents frequently in infected individuals as neuronal dysregulation and cognitive deficits, especially involving motivation and reward-related decision making. Interestingly, neuronal cannabinoid type-1 receptors (CB1R) are upregulated when exposed to HIV-1 viral proteins including transactivator of transcription (Tat), one of the most neurotoxic viral proteins associated with latent HIV-1 infection. The endogenous cannabinoid system is a promising therapeutic target as activation reduces inflammation and restores neuronal function in models of nervous system insult. Indeed, previous studies have shown reductions in measures of inflammation by inhibiting degradation of 2-arachidonoylglycerol (2-AG), an endocannabinoid produced to promote cellular responses to damage in tissue or neighboring cells and regulate activity of neurons. In exploring the protective effects of endogenous cannabinoid activity modulation against toxicity driven by Tat, we have previously found that upregulating 2-AG through blocking its breakdown using monoacylglycerol lipase inhibitor MJN110 is neuroprotective in models of Tat-induced neural and cognitive dysregulation in vitro and in vivo, respectively. Given these findings, I hypothesize that inhibiting hydrolysis of 2-AG in vivo may downregulate Tat-driven neuronal excitotoxicity during reward-related behavior and reduce proinflammatory markers in brain tissue. However, the effects of Tat and MJN110 have not yet been characterized using in vivo imaging. Thus, the goal of this project is to determine how Tat and MJN110 influence excitability of neurons and corresponding behavior, expression of proinflammatory cytokines IL-6 and IL-8, as well as density of cannabinoid type-1 receptors (CB1R) on neurons and microglia in the following two Specific Aims. Aim 1. To use in vivo one-photon microscopy during a reward-related behavioral task to characterize activity patterns of dorsomedial prefrontal cortex neurons in the presence of Tat and/or MJN110. Aim 2. To use immunohistochemical labeling and multiplex assays to determine whether MJN110 is able to reduce cell-specific CB1R density or proinflammatory cytokine expression, respectively. In doing so, I will enhance our understanding of endocannabinoid therapeutic potential against neuronal dysfunction and inflammation which underlie complications associated with latent HIV-1 infection.