Meeting Abstract

89.2  Monday, Jan. 6 13:45  Changes in glucocorticoid and mineralocorticoid receptor mRNA expression during the short arctic breeding season in a free living wild song bird the Gambel’s White-crowned Sparrow KRAUSE, JS*; MCGUIGAN , MA; WINGFIELD, JC; MEDDLE, SL; Univ. of California, Davis; Univ. of California, Davis; Univ. of California, Davis; Univ. of Edinburgh jskrause@ucdavis.edu

Every spring, migratory songbirds leave their wintering grounds to travel to breeding grounds where they can encounter demanding situations such as intense storms, food shortages, predation and social disputes. During such times, songbirds are reliant upon the hypothalamic pituitary adrenal (HPA) axis and the production of the stress hormone, corticosterone (CORT), to induce changes in behavior and physiology to promote survival. In many high latitude breeding songbirds, the stress response is higher during arrival on their breeding territories compared to the parental phase. The reduction in the stress response is critical for preventing nest abandonment and ensuring parental investment but little is known about the neural regulation of this adaptation. This study investigated changes in the expression of mRNA for the two CORT receptors termed the mineralocorticoid receptor (MR) and the glucocorticoid receptor (GR) in the brain of male Gambel’s White-crowned sparrows using in situ hybridization. There was a significant decline in MR mRNA expression in the hippocampus when birds at the preparental phase were compared to those in the parental phase; no significant change was found in GR in the paraventricular nucleus. Changes in MR and/or GR expression may be critical for regulating negative feedback and thus controlling both baseline and stress induced levels of CORT. These data suggest that changes in MR sensitivity may be important for regulating the stress response in birds that have very short breeding seasons at high latitude.