Cross-talk between the Oxytocin and Vasopressin Systems in the Brian: Roles in Social Behavior

Oxytocin (OT) and arginine vasopressin (AVP) are closely related nine amino acid neuropeptides primarily produced in the hypothalamus and released both in the peripheral and central nervous systems. For over 100 years, OT and AVP have been known for their roles in uterine contraction/milk letdown and blood vessel constriction, respectively. Over the past few decades, the roles of OT and AVP in the central nervous system have been extensively investigated in the regulation of a variety of complex social behaviors including sex, parenting, pair bonding, social play, and aggression. High levels of structural similarities exist between OT and AVP and between the OT and AVP1a receptor. Interestingly, there is little data on whether cross-talk between the OT and AVP systems occurs in the central nervous system. Therefore, the goal of this dissertation is to examine cross-activation of OT receptors by AVP and of AVP1a receptors by OT, and the functional significance of this cross-talk in the regulation of social behavior. Three specific aims are addressed using Syrian hamsters as animal models: Aim 1 was to test the hypothesis that central OT enhances social communicative behavior by acting on V1aRs; Aim 2 was to test the hypothesis that central OT and AVP prolong social recognition via activation of the same receptor, OTRs or V1aRs. Aim 3 was to test the hypothesis that AVP in the ventral tegmental area (VTA) enhances social reward via activation of OTRs. Our data showed intraccerebroventricular (ICV) injections of OT or AVP act on V1aRs to induce social communication; ICV injections of OT and AVP act on OTRs to prolong social recognition; OT and AVP in the VTA act on OTRs and not V1aRs to enhance social reward. These results demonstrate the ability of OT and AVP to facilitate three essential aspects of a social interaction: communication, recognition, and reward. Our findings also strongly suggest OT and AVP act on both OTRs and V1aRs to influence social behavior but that OTRs regulate some social behaviors while V1aRs regulate other social behaviors. INDEX WORDS: Social communication, Social recognition, Social reward, Prosocial behavior, Syrian hamsters, Aggression CROSS-TALK BETWEEN THE OXYTOCIN AND VASOPRESSIN SYSTEMS IN THE BRAIN: ROLES IN SOCIAL BEHAVIOR