Activation of Npas1-neurons in the Ventral Pallidum Mediates Stress Susceptibility

Background: Altered activity of the ventral pallidum (VP) underlies disrupted motivation after stress exposure. The VP is a very heterogeneous structure comprised of many different neuron types with distinct electrophysiological properties and projections. Neuronal PAS 1-positive (Npas1+) VP neurons are thought to send projections to brain regions critical for stress response. In this study, we evaluated how activity of VP Npas1+ neurons affect emotional behaviors and responses to social stress. Methods: We used a chemogenetic approach to manipulate VP Npas1+ neurons during social defeat stress (SDS) and behavioral tasks related to anxiety and motivation in Npas1-Cre mice. We employed a similar approach in females using the chronic witness defeat stress (CWDS). Finally, to characterize VP Npas1+ neuron circuitry and molecular identity we evaluated the projection targets of the VP Npas1+ neurons and performed RNA-seq on ribosome-associated mRNA from VP Npas1+ neurons. Results: Chemogenetic activation of VP Npas1+ neurons increased susceptibility to a subthreshold (S)SDS and anxiety-like behavior in the elevated plus maze and open field. Inhibition of VP Npas1+ neurons enhanced resilience to chronic (C)SDS and CWDS. We identified VP Npas1+ projections to the nucleus accumbens (NAc), ventral tegmental area (VTA), medial and lateral habenula (LHb), lateral hypothalamus (LH), thalamus, medial and lateral septum, and periaqueductal gray area. VP Npas1+ neurons displayed distinct transcriptomes representing distinct biological processes. Conclusions: Activity, of VP Npas1+ neurons, modulates susceptibility to social stressors and anxiety-like behavior. These outcomes could be related to their projections to brain regions that modulate reward and aversion.