Meeting Abstract

P2.157  Sunday, Jan. 5 15:30  The role of testosterone and vasotocin on the stress response of male passerines GAO, S*; LANE, S; VALLE, S; DEVICHE, P; Arizona State University, Tempe sisi.gao@asu.edu

In many seasonally reproducing birds, the stress response and plasma testosterone (T) vary according to reproductive condition. In rodents, plasma T regulates the stress response through vasopressin. In birds, studies have examined the interactive effect of both T and vasotocin (AVT; the avian vasopressin) on the stress response only in domesticated species, and have yielded conflicting results. We hypothesized that T and AVT regulate this response in adult male House Sparrows (Passer domesticus). During the non-breeding (January) and breeding (March, May) seasons, we caught birds, rapidly collected blood (baseline, BL), restrained them for 30 min, and collected a second blood sample (stress-induced, SI). Plasma CORT increased in response to stress throughout the year, but less so in January than during the spring, thereby confirming seasonal changes in the stress response. Plasma BL T was lower in winter than spring and, irrespective to season, always decreased during stress. To test if T and AVT regulate the stress response, captive males in non-reproductive condition received empty (control), 3 mm-long, or 6 mm-long T-filled Silastic capsules to result in low, medium, and physiologically high plasma T. Over the following 6 weeks, each bird was bled immediately after removal from its home cage (BL), received an iv injection of AVT [control, low (1.5 µg/kg), high (3 µg/kg)], was restrained for 30 min, and then bled again (SI). Neither T treatment nor AVT injection affected plasma BL or SI CORT. These observations do not support the hypothesis that seasonal changes in the stress response are T or AVT-regulated and with previously published studies, suggest that this regulation may be species- and/or environment-specific. Supported by National Science Foundation Award 1026620 to P.D.