P2.181  Thursday, Jan. 5  A new view of the stress response in free-living birds: 3-way adrenal steroid response KRAUSE, J.S.*; DORSA, D; WINGFIELD, J.C.; University of California, Davis; University of California, Davis; University of California, Davis jskrause@ucdavis.edu

To better understand the integrated response to capture stress through the increased plasma levels of three major adrenal steroids – corticosterone (Cort), dehydroepiandrosterone (DHEA) and progesterone – we present data from our recently developed protocol for partition chromatography that effectively separates the steroids from a single plasma sample of <100ul in 3 taxa of Zonotorichia sparrows. Following separation, quantification of each steroid was determined by specific radioimmunoassay (RIA). As is well known, the stress response is the activation of the hypothalamo-pituitary-adrenal (HPA) axis in reaction to unpredictable events, which allows organisms to cope behaviorally and physiologically to the disruption. To date, most studies have focused on Cort as the major stress hormone; however DHEA and progesterone are also synthesized and released into the blood stream and thought to modify the stress response. DHEA has been widely implicated to have anti-stress properties that may decrease the severity of the stress response if levels rise during the stressor. If progesterone levels rise, Cort may be displaced from corticosterone binding globulin (CBG) due to its higher affinity for progesterone than for Cort. This would result in displacement of Cort from CBG and increase plasma levels of free cort that could modify the stress response further. To test these ideas while developing our chromatographic procedures, we utilized a standard capture and restraint protocol in wintering populations of white crowned sparrows (Z. l. gambelii and Z.l. nuttalli) and golden crown sparrows (Z. atricapilla). Our results indicate support for the involvement of these 3 steroids in the stress response and further our understanding of how organisms cope with unpredictable events.