Amygdala AVPR1A mediates susceptibility to chronic social isolation in female mice

Sex differences in responsiveness to social stress in adulthood are highly conserved across species, with females more sensitive to isolation. Here, we show that Arginine vasopressin receptor 1a (AVPR1A) in the central nucleus of the amygdala (CeA) mediates the enhanced susceptibility of females to post-pubertal chronic social isolation stress (CSIS) in mice. Chemogenetic activation of AVPR1A^CeA circuits induces anxiety-related behaviors in both sexes. However, genetic, pharmacological, chemogenetic and optogenetic loss of function approaches support the idea that it is only endogenously engaged in females in the context of CSIS. Using a combination of virus-based tools, we identified a major source of AVP ligand in the posterodorsal part of the medial amygdala (MePD) as well as an important downstream target of AVPR1A^CeA neurons, the dorsolateral striatum (DLS). Loss of function approaches identified three nodes in the circuit that provide sex-specificity in the effects of CSIS on anxiety-related behaviors: 1) ERα signaling in AVP^MePD neurons; 2) engagement of the AVPR1A pathway in the CeA; and 3) number of AVPR1A^CeA projections to the DLS. These data support new therapeutic applications for AVPR1A antagonists in women experiencing social isolation or loneliness.