NEPHEW, B.C.*; ROMERO, L.M.: Peripheral arginine vasotocin (AVT) increases corticosterone, but decreases behavior in European Starlings (Sturnus vulgaris)

The neurohormone arginine vasotocin (AVT) has been shown to have diverse effects on numerous avian behaviors including vocalization, learning, sexual behavior, aggression, and general activity level. It is unclear whether these effects are modulated by AVT alone, AVT-induced increases in corticosterone concentrations, or by an interplay of both hormones. To test this relationship, AVT was administered peripherally to European Starlings (Sturnus vulgaris ) and the ensuing endocrine and behavioral effects were monitored. Four doses of AVT (0.5, 1.0, 4.0, 8.0ug) were injected subcutaneously and starling behavior was videorecorded for 55 minutes. AVT caused significant decreases in feeding, drinking, preening, and perch hopping behavior in a dose-dependent manner. In a second experiment starlings were injected with 0.5, 4.0, and 8.0ug AVT, and 30 minute post-injection blood samples were collected for analysis of corticosterone concentrations by radioimmunoassay. Although the 4.0 and 8.0ug doses resulted in elevated corticosterone concentrations, the 0.5ug AVT dose elicited behavioral effects in the absence of a significant rise in plasma corticosterone concentrations. These results suggest that systemic AVT may gain entry to the brain and act as a potent neurohormone in starlings independent of its stimulatory role in adrenocorticotropin release.