Meeting Abstract

31.5  Jan. 5  Chronic stress alters the avian cardiovascular and glucocorticoid stress response CYR, N.E.*; ROMERO, L.M.; Tufts University; Tufts University npoiri01@tufts.edu

The activation of the stress response to noxious stimuli is essential to survival in animals, however long term activation of the stress response may have critical medical and physiological consequences. To better understand the hormonal and cardiovascular changes caused by stress, we implanted heart monitors into wild caught European starlings, Sturnus vulgaris, and measured heart rate (HR) and corticosterone (CORT, the primary avian stress hormone) under baseline, acute stress, and chronic stress conditions. To induce chronic stress we used a chronic stress protocol (CSP) consisting of 5 stressors (loud radio, cage tapping, cage rolling, novel voice, and bag restraint) administered randomly for 30 min for 4 times/day over 16 days. In birds, the catecholamines epinephrine and norepinephrine both bind to &beta -adrenoceptors to mediate HR. We injected propranolol (&beta -adrenoceptor blocker) into 7 acutely stressed birds and in 8 chronically stressed birds to determine the &beta -adrenoceptor mediated changes in HR during acute and chronic stress. We found that both body weight and CORT decreased throughout chronic stress, which mirrors the results of a previous study in starlings. The CSP altered both basal and acute stress-induced HR. The 24 hour basal HR cycle immediately following the CSP was significantly lower than prior to the CSP. Basal HR at night decreased throughout the CSP and increased following its completion. In contrast, Basal HR during mid-morning increased at the end of the CSP. Restraint-induced tachycardia increased at the beginning of the CSP, but then significantly decreased at the end of the CSP. Propranolol caused a significant decrease in HR during acute stress, but only slightly decreased tachycardia in chronically stressed birds most likely because the HR response was already damped. Overall, the cardiovascular stress response was significantly altered in chronically stressed birds.