Hypothalamic-amygdala gating of caregiving-like prosocial behavior in mice.

Distress sharing within an ingroup instinctively motivates caregiving-like prosocial behavior in social animals and humans, yet how aversive social stimuli paradoxically trigger such behavior remains unclear. Here, we show that stress-state matching in observer mice elicits caregiving-like behaviors (allogrooming and injury-targeted allolicking) toward cagemates in pain, resulting in synchronized social buffering. Importantly, we identify that the excitation of vasopressin receptor 1a-expressing (V1aR-expressing) neurons in the central medial amygdala (CeM) underlies both emotional-state matching and subsequent allogrooming/allolicking. This excitation is accomplished by arginine vasopressin (AVP) release from presynaptic terminals of the hypothalamic paraventricular nucleus (PVN) to act specifically on postsynaptic V1aR in the CeM. The CeMV1aR neurons then project to the ventral tegmental area (VTA) to drive caregiving-like actions through positive reinforcement, manifested as prosocial preference and recurrent allogrooming/allolicking, and to produce anxiolysis in the caregiver. Collectively, we unravel a dedicated trisynaptic PVNAVP-CeMV1aR-VTA circuit driving and gating caregiving-like behaviors and advance the mechanistic understanding of AVP-V1aR signaling in prosociality.