114.6 Saturday, Jan. 7 Effects of chronic stress on brain and peripheral intracellular glucocorticoid receptors in wild House Sparrows LATTIN, Christine R.*; MEDINA, Carlos; ROMERO, L. Michael; Tufts University; Tufts University; Tufts University firstname.lastname@example.org
Glucocorticoids such as corticosterone (CORT) are essential in helping wild animals cope with environmental stressors, but sustained high concentrations of these hormones can cause many negative effects. Most studies of chronic stress have focused on hormone titers; some studies have found higher baseline CORT in response to presumed chronic stressors, whereas others have found a decrease. This diversity of results means it is not possible to simply look at plasma CORT and distinguish between healthy and compromised animals, nor to predict exactly what effects chronic stress may have on the animal. To help clarify the effects of chronic stress, we looked “downstream” of hormones at intracellular CORT receptors in the brain and periphery. We captured 45 wild House Sparrows and divided them into two groups: a control group (n=20) to control for the effects of long-term captivity, and a stressed group (n=25) subjected to a 3-week chronic stress protocol (CSP) in the lab. Birds were sacrificed before the start of the CSP, every week during the CSP, and following 1 week of recovery. Mineralocorticoid receptors (MR) and glucocorticoid receptors (GR) were quantified using radioligand binding assays. In whole brain, there was no difference in GR between control and stress birds, or during the recovery period. However, MR was higher in stressed birds during the CSP than in control birds (81.0±7.1 fmol binding/mg protein and 58.9±7.1 fmol binding/mg protein, respectively; p=0.035). During the recovery period, MR in stressed birds decreased back to control levels. Preliminary results suggest there was no difference in liver GR or MR between control and stressed birds. These results are consistent with the idea that chronic stress may affect animals in a species- and tissue-specific manner.