P2.174 Thursday, Jan. 5 Seasonal Variation of Glucocorticoid Regulation in House Sparrows (Passer domesticu) LIEBL, A.L.*; MARTIN, L.B.; University of South Florida email@example.com
Many animals demonstrate distinct seasonal variation in baseline glucocorticoids (GCs), release in response to stressors, and adrenal sensitivity to corticotrophins. However, whether the capacity to down-regulate GCs or the expression of the mineralocorticoid receptor(MR) or glucocorticoid receptor (GR), receptors integral to GC regulation, vary seasonally has been studied less. Whereas MR is predominantly responsible for maintain baseline levels, GR controls negative feedback of GCs. Here, we measured GCs at baseline, after exposure to a restraint stressor, and in response to negative feedback (pharmacologically induced by dexamethasone) as well as GR and MR expression in hippocampus in wild house sparrows (Passer domesticus). GCs were measured during both breeding and molt, as GC release and adrenal sensitivity differs between these two seasons in sparrows. Consistent with previous studies, restraint-induced GCs were suppressed during molt when compared to breeding. Interestingly, despite considerable variation, birds were only able to down-regulate GCs during the breeding season. Neither MR nor GR expression was correlated with hormone titers during molt, but this could be an artifact of a dampened up and down regulation of the hormone. We predict correlations between GR and capacity to down-regulation GCs during the breeding season; analysis is ongoing.