The behavioral neurobiology of affiliation and paternal care in Microtus pennsylvanicus (meadow voles)

Central nervous system (CNS) arginine-vasopressin (AVP) and oxytocin (OT) receptor patterns are associated with interspecific social organization in voles (Microtus). Monogamous voles show more AVP and OT receptor binding in the extended amygdala than non-monogamous voles. However, non-monogamous meadow voles exhibit seasonal changes in social organization that may reflect seasonal differences in mating and parenting strategies. The goals of this dissertation were to determine (1) whether meadow voles were capable of displaying selective partner preferences and paternal behavior, and (2) whether AVP and OT were involved in male parental behavior and female partner preference formation. Data from chapter two established that male and female meadow voles rapidly form selective opposite-sex partner preferences following 24 h of cohabitation, and these preferences are comparable to those reported for monogamous prairie voles. Data from chapter three suggest that photoperiod strongly influences paternal behavior. Specifically, males housed in short day lengths exhibit proportionally more and qualitatively better paternal care than males housed in long day lengths. Experiments in chapter four determined that CNS administration of AVP suppresses pup-directed aggression in previously aggressive males, promotes paternal behavior in previously non-paternal males, and CNS administration of a V1a AVP antagonist blocks the onset of paternal behavior. Experiments in chapter five demonstrated that distribution of AVP and OT receptors in the extended amygdala covary with paternal state. Finally, data from chapter six revealed that CNS OT receptor patterns covary with seasonal changes in intraspecific social behavior and partner preference onset in females, i.e., partner preference formation corresponds with greater OT receptor binding in the extended amygdala. Taken together, data from these five chapters suggest that AVP and OT receptors in the extended amygdala are associated with seasonal differences in intraspecific social organization and possibly life history strategies differentially associated with fall and summer breeding conditions in meadow voles. Additionally, these experiments are the first to suggest a role for CNS OT in regulating parental care in male mammals, and the first to show a relationship between the development of partner preferences and regional CNS OT receptor patterns in female mammals.