BOYD, E.H.*; BUSCH, D.S.*; WINGFIELD, J*; University of Washington: Affects of Intermittent Increases in Corticosterone in the White-Crowned Sparrow
When vertebrates experience perturbations, the hypothalamo-pituitary-adrenal axis is activated causing glucocorticoid secretion to increase followed by a cascade of physiological events. These include suppression of reproduction and regulation of the immune system. While these events promote survival in response to acute perturbations, they can be deleterious in the long term. One important question in basic biology and conservation is when do repeated acute stressors become chronic stress? We tested whether frequent intermittent increases in corticosterone can have effects similar to chronic stress. White-Crowned Sparrows were exposed to 20 hours of light and 4 dark per day with food and water ad lib. Birds were treated 3 times daily for 3 weeks with a topical solution of 10 ug corticosterone in 20 ul DMSO or 20 ul DMSO as a control. A separate group was undisturbed. There was no affect of treatment on gonad size, as determined by laparotomy, but there was a decline in health compared with the control and undisturbed groups. Four of eight corticosterone treated birds developed bacterial infections including three with a mild anemia consistent with anemia of chronic disease and two had leukocyte counts outside the normal range. Of these birds only one showed an increased leukocyte count in response to infection. This decline in health is consistent with chronic immune suppression. These results show that intermittent increases of corticosterone simulating acute stress responses id frequent can cause deleterious effects associated with chronic stress.
