Endocannabinoid modulation of behavioral engagement via an aPVT-NAc circuit - Substance use disorders (SUD) are characterized by pathological behavioral engagement with rewarding stimuli despite negative outcomes. There has been a concerted effort to identify the neural correlates of reward receipt, as well as the systems-level processes that govern chronic cannabis use disorders, a growing problem in the US. There remains a lack of mechanistic understanding of the intrinsic neurobiology which underlies behavioral engagement, a fundamental process in drug seeking behavior. As such, the primary goal of this pathway to independence proposal will be to receive in depth neuroscience training, facilitating new skills in a series of cutting-edge approaches which will provide a deeper understanding of the underpinnings of neuromodulatory regulation of engagement in reward-seeking behaviors, and how these mechanisms are altered with chronic cannabinoid use. The Nucleus Accumbens(NAc) represents an important reward network hub known to regulate reward engagement and the reinforcing properties of drugs of abuse. The NAc receives dense innervation from the Paraventricular Thalamus(PVT), which receives visceromotor and interoceptive inputs from the hypothalamus and hindbrain, and projects widely across the forebrain to regulate a variety of motivated behaviors. The PVT is a highly heterogenous structure, and recent studies examining the PVT-NAc circuit have shown conflicting results, partially driven by a lack of genetic and anatomical specificity within the PVT. The neuromodulatory peptide neurotensin(NTS) is selectively expressed in the anterior PVT and our preliminary data demonstrates that these neurons send excitatory projections to the NAc, which are enriched with the cannabinoid 1 receptor(CB1R) and tightly regulated via endogenous cannabinoid(eCB) signaling. In this proposal, we first aim to understand how eCB modulation of aPVT projections to the NAc regulates behavioral engagement. Our preliminary experiments demonstrate that aPVT projections to the NAc are inhibited during behavioral engagement and excited upon disengagement, in both rewarding and aversive contexts. In tandem with our electrophysiology data demonstrating retrograde eCB inhibition of PVT terminals, we will determine when and how eCBs are released in vivo to modulate aPVT input to ultimately affect behavioral engagement. Our second aim will be to determine how the activity of projection defined NAc neurons is causally linked to eCB production and reward seeking behavior. In this aim, we will use 1-photon imaging to record the activity of specific aPVT-NAc projection ensembles. We will multiplex this high-resolution neural data with novel machine learning behavioral tracking algorithms to directly correlate neural activity with discrete aspects of reward seeking behaviors. Finally, in the R00 portion of this grant, I will expand the scope of this study to other aPVT output regions to determine how the aPVT regulates cannabinoid seeking behaviors through divergent efferent projections across the forebrain. The training received under this proposal will facilitate my transition to heading my own independent academic research laboratory focused on decoding neuromodulation in SUD.
