Central vasopressin administration regulates the onset of facultative paternal behavior in Microtus pennsylvanicus (Meadow voles)

Pharmacological experiments have implicated a role for central arginine vas opressin (AVP) in regulating paternal behavior in monogamous prairie voles. Although nonmonogamous meadow voles exhibit appreciable paternal care when housed under winter, short day lengths (SD), no research has examined whet her the same neurobiological systems are involved in regulating paternal be havior in a nonmonogamous species when it behaves paternally. The goal of t hese experiments was to determine whether central administration of AVP, bu t not cerebrospinal fluid (CSF), affected the suppression of pup-directed a ggression and/or the onset of paternal behavior in meadow voles. Data from experiment 1 implicated a role for AVP in facilitating changes in male beha vior: central administration of 1 ng of AVP (but not 3 ng or CSF) inhibited pup-directed aggression in previously pup-aggressive males, and 3 ng of AV P (but not 1 ng or CSF) induced paternal behavior in previously nonpaternal males. In contrast, AVP (1 and 3 ng) did not enhance paternal behavior in already paternal males. Experiment 2 tested the specificity of AVP. Previou s research indicated that 24 h of unmated cohabitation with a female reliab ly induced paternal behavior in SD males. Hence, experiment 2 examined whet her administration of a V-1a AVP antagonist (AVPA), but not CSF, prior to 2 4 h of unmated cohabitation would block the onset of paternal behavior. Mal es that received CSF displayed paternal behavior faster and engaged in more investigatory and paternal behaviors than males that received AVPA. Thus, pharmacological experiments support the hypothesis that AVP likely regulate s paternal behavior in both facultatively and consistently paternal vole sp ecies. (C) 2001 Academic Press.