Sex and Stress Govern the Function and Innervation of a Basolateral Amygdala to Nucleus Accumbens Corticotropin-Releasing Hormone/GABA-Expressing Projection.

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 long-range corticotropin-releasing hormone (CRH)/GABA-expressing projection from the basolateral amygdala (BLA) to the nucleus accumbens (NAc) that mediates reward-seeking deficits in adult ELA males-but not females. 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 the BLA and clozapine-N-oxide or vehicle to the NAc medial shell during reward behaviors. Using tissue clearing, light sheet fluorescence microscopy, and deep learning pipelines, we mapped brain-wide CRH+/GABA BLA axonal projections to identify potential sex differences in its innervation. Chemogenetic manipulations in male mice demonstrated inhibitory effects of the CRH+/GABA 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. In 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. 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-dependent impacts of ELA on reward behaviors.