Meeting Abstract

P3.164  Tuesday, Jan. 6  Cortisol and corticosterone in the avian immune and nervous systems during development SCHMIDT, Kim L*; CHIN, Eunice H; SHAH, Amit H; SOMA, Kiran K; Univ. of British Coulmbia; Trent Univ.; Michigan State Univ.; Univ. of British Coulmbia kschmidt@interchange.ubc.ca

Glucocorticoids (GCs) have important effects on the developing immune and nervous systems. In addition to being synthesized by the adrenal glands, GCs may be synthesized in extra-adrenal tissues, including the immune system and brain. In developing zebra finches, cortisol levels in the immune system are higher than cortisol levels in plasma, and cortisol (not corticosterone) is the predominant GC in the immune system (Schmidt and Soma, 2008). To date, little is known about how local GC production differs among species and how it varies with life history strategy. Songbirds provide the opportunity for comparative studies of local GC production. Here, in study 1, we measured cortisol and corticosterone in the plasma, immune system (bursa, thymus, spleen) and brain of European starlings at post-hatch day 0 (P0) and P10. Subjects were sampled within 3 min or after 45 min of restraint. In study 2, we directly compared local GC levels in zebra finches and starlings at the same age. Steroids were extracted using solid phase extraction and quantified using specific and sensitive immunoassays. Surprisingly, in study 1, GC levels in the immune system were comparable to GC levels in the plasma of starlings. GC levels in the brain were lower than GC levels in plasma. Restraint increased local and systemic GC levels at P10, but not at P0. In study 2, in zebra finches, cortisol was the predominant GC in the immune system, and cortisol levels in the immune system were higher than cortisol levels in plasma. In starlings, cortisol levels were lower in the immune system, suggesting a species difference in local cortisol synthesis. In both species, GC levels in the brain were low. These results suggest a species difference in systemic and local GC levels, which may be due to differences in the life history strategies of zebra finches and starlings.