Meeting Abstract
The 11-β-Hydroxysteroid Dehydrogenase (11-β-HSD) system has been hypothesized to be a key regulatory step in local signaling and in controlling seasonal changes in corticosterone in free-living birds. 11-β-HSD Type 1 catalyzes local corticosterone production and 11-β-HSD Type 2 catalyzes local deactivation of corticosterone. We tested the hypothesis that 11-β-HSD can affect stress induced corticosterone, and this would provide a means for understanding mechanisms underlying seasonal changes in stress physiology in male white-crowned sparrows (Zonotrichia leucophrys). We measured the effectiveness of two separate and specific 11-β-HSD antagonists systemically in the field and centrally into the third ventricle in a laboratory experiment. Inhibition of Type 1 using metyrapone produced mixed results with systemic injections showing measurable decreases with integrated area under the curve (AUC) analyses, while no differences were detected for injections into the third ventricle. Inhibition of Type 2 with diethyldithiocarbamate resulted in elevated corticosterone (AUC) for both systemic and central infusion. Our study suggests plasma corticosterone may be regulated peripherally by Type 1 and centrally by Type 2. As life history stage or other factors could influence 11-β-HSD dynamics throughout the annual cycle, we use caution in this interpretation. Further investigations are needed to fully understand the importance of the 11-β-HSD system in regulating corticosterone in free-living birds.
