Cortical mechanisms of opioid reinforcement

PROJECT SUMMARY This application outlines a program of research designed to better understand the molecular, cellular, and circuit- based mechanisms of opioid use disorder (OUD). We recently showed that μ opioid receptors (μORs) are densely expressed by neurons in the dorsal peduncular nucleus (DPn) of the ventral prefrontal cortex. Genetic ablation of μORs from DPn neurons abolished the rewarding effects of opioids and instead rendered opioids highly aversive. Disrupting μOR signaling in the DPn also exacerbated the severity of physical and affective components of the opioid withdrawal syndrome, while chemogenetically silencing neural activity in the DPn attenuated opioid withdrawal. Single-cell and spatial transcriptomics showed that μORs in the DPn are expressed by an atypical population of cortical pyramidal neurons that also express vesicular glutamate transporter 2, which densely innervate the parabrachial nucleus (DPnvGlut2àPBn neurons). These exciting new findings suggest that DPnvGlut2àPBn neurons play critical roles in the behavioral actions of opioids that drive the development of OUD. In this application, we will use cutting-edge molecular, cellular, and behavioral approaches to investigate the role of DPnvGlut2àPBn neurons in the motivational properties of opioids. In AIM 1, we will use intersectional genetics strategies to manipulate the expression of μORs in only DPnvGlut2àPBn neurons and thoroughly investigate the consequences on intravenous (IV) opioid self-administration behavior. In AIM 2, we will use whole-cell electrophysiological recordings combined with single-cell sequencing (PATCH-seq) to define the molecular identity of the PBn neurons that receive direct excitatory synaptic input from DPnvGlut2 neurons (PBnDPn neurons). We will then chemogenetically manipulate the activity of these PBnDPn neurons and determine the consequences on IV opioid self-administration behavior. In AIM 3, we will use single-nuclei RNA sequencing (snRNA-seq), single-nuclei spatial transcriptomics, and whole-cell electrophysiological recordings to define the transcriptional and function adaptations that occur in DPnvGlut2 and PBnDPn neurons during the development of opioid dependence. We will also investigate the behavioral consequences of chemogenetically manipulating the activity of DPnvGlut2 and PBnDPn neurons on the expression of physical and affective components of the opioid withdrawal syndrome. This highly innovative program of research builds on exciting new findings from our laboratory and promises to yield fundamentally new insights into the neurobiological mechanisms of opioid addiction.