Fig. 4 |. The corticotropin-releasing factor system and oxytocin interact to maintain the pair bond.

, a | Effect of loss of the partner on the corticotropin-reieasing factor (CRF) and oxytocin (OT) signalling in the nucleus accumbens (NAc). Separation from the partner results in decreased OT synthesis in the paraventricular nucleus (PVN) and a reduction of OT receptors (OXTRs) in the NAc. Upon separation from the partner, CRF or the related urocortins (UCN 1,2 and 3) are released in the NAc, binding to CRF type 2 receptors (CRFR2) on OT terminals and inhibiting OT release. Thus, separation from the partner leads to decreased OT signalling through multiple mechanisms, b |The forced swim test is a behavioural assay in which an increased amount of time spent passively floating indicates a depressive-like state. Male voles paired with their partner spent little time floating, but this time increased upon separation from their partner. This social-loss-induced behaviour was eliminated by local infusion of the CRFR2 antagonist into the NAc.c | Infusion of OT into the NAc also eliminates the increase in passive floating in the forced swim test. Infusion of the OT antagonist into the NAc increases the floating behaviour in males even when they remain paired. Thus, the withdrawal of OT signalling following separation may maintain bonds by creating an aversive emotionalstate. Part b adapted from REF.¹¹⁵, Springer Nature Limited. Part c adapted with permission from REF¹²⁰, Elsevier.