Alterations in hypothalamic-pituitary-adrenal function associated with captivity in Gambel's white-crowned sparrows (Zonotrichia leucophrys gambelii)

Gambel's white-crowned sparrows were captured and brought into captivity in order to study seasonal changes in the function of the hypothalamic-pituit ary-adrenal (HPA) axis in captive birds. 30 min of restraint elicited a ris e in corticosterone titers that varied depending upon the season and physio logical state of the birds. Restraint elevated corticosterone liters signif icantly more during the fall (within 2 weeks of capture from the wild) than during either the winter or during a prealternate or prebasic molt. We als o examined what changes in the HPA axis could account for altered corticost erone levels. Exogenous ACTH significantly elevated corticosterone levels b eyond the response to restraint during the fall, indicating a dramatic enha ncement of the adrenal's ability to secrete corticosterone. Exogenous ACTH was ineffective at other limes, suggesting that the adrenal's ability to re lease corticosterone often limits circulating levels. We further inferred t he pituitary's ACTH secretory ability by injecting exogenous corticotrophin -releasing factor, arginine vasotocin, and mesotocin and measuring corticos terone release: Pituitaries failed to respond to any exogenous releasing fa ctor during the fall, suggesting that the pituitary may be the site in the HPA axis regulating corticosterone release at this time. When compared to w ild-caught birds, these results suggest that captivity alters both adrenal and pituitary function during restraint in white-crowned sparrows, and that this change depends upon the season and/or physiological state of the anim al. Captivity thus appears to have a profound affect on the function of the HPA axis, and these results reiterate the caution that must be used to ext rapolate laboratory data to field conditions. (C) 1999 Elsevier Science Inc . All rights reserved.