Sex-and Stress-Dependent Plasticity of a Corticotropin Releasing Hormone / GABA Projection from the Basolateral Amygdala to Nucleus Accumbens that Mediates Reward Behaviors

Background: Motivated behaviors are executed by refined brain circuits. Early-life adversity (ELA) is a risk for human affective disorders involving dysregulated reward behaviors. In mice, ELA causes anhedonia-like behaviors in males and augmented reward motivation in females, indicating sex-dependent disruption of reward circuit operations. We recently identified a corticotropin-releasing hormone (CRH) expressing GABAergic projection from basolateral amygdala (BLA) to nucleus accumbens (NAc) that governs reward-seeking deficits in adult ELA males, but not females. Methods: To probe the sex-specific role of this projection in reward behaviors, adult male and female CRH-Cre mice raised in control or ELA conditions received excitatory or inhibitory Cre-dependent DREADDs in BLA, and then clozapine N-oxide or vehicle to NAc medial shell during reward behaviors. We determined the cell identity of the projection using immunostaining and electrophysiology. Using tissue clearing, light sheet fluorescence microscopy and deep learning pipelines, we mapped brain-wide BLA CRH+ axonal projections to uncover sex differences in innervation. Results: Chemogenetic manipulations in male mice demonstrated inhibitory effects of the CRH+ BLA-NAc projection on reward behaviors, whereas neither excitation nor inhibition influenced female behaviors. Molecular and electrophysiological cell-identities of the projection did not vary by sex. By contrast, comprehensive whole-brain mapping uncovered significant differences in NAc innervation patterns that were both sex and ELA-dependent, as well as selective changes of innervation of other brain regions. Conclusions: The CRH/GABA BLA-NAc projection that influences reward behaviors in males differs structurally and functionally in females, uncovering potential mechanisms for the profound sex-specific impacts of ELA on reward behaviors.