Meeting Abstract
Individuals in urban habitats experience frequent disturbances and are expected to respond efficiently and recover quickly from challenges to persist in these habitats. The glucocorticoid (GC) stress response is a physiological response to a stressor during which GC concentration increases in order to activate behavioral and physiological mechanisms to recover homeostasis. Differences in the duration of GC secretion are modulated by the efficiency of negative feedback mechanisms, which is achieved primarily through the binding of glucocorticoid receptors (GRs) in the hippocampus by GC’s. Efficient termination of the GC stress response could protect birds in urban habitats from chronic GC exposure. We investigated if male song sparrows (Melospiza melodia) in urban habitats show more efficient negative feedback of the GC stress response than their rural counterparts. Song sparrows from each habitat were exposed to restraint stress to increase corticosterone (CORT), the primary avian GC, then injected with either saline or a synthetic GC (dexamethasone, DEX), to induce a negative feedback response. Additionally, we quantified GR mRNA in the hippocampus using qPCR in a separate cohort of birds. Our results show that DEX suppressed CORT concentration below that of saline, but no habitat differences in response to DEX were detected. Urban song sparrows did have lower hippocampal mRNA levels of GR than rural song sparrows. Urbanization therefore does not affect the GC stress response, but can cause structural changes in the hippocampus, the functional effects of which remain to be elucidated.
