Meeting Abstract
For over 50 years, dexamethasone (Dex) has been the predominant synthetic glucocorticoid used to test hypothalamic-pituitary-adrenal negative feedback strength. While Dex works in a majority of systems, it is only a single example of a much larger class of synthetic glucocorticoids used as drugs, each with unique structures. Several other drugs are now readily available and could potentially more strongly stimulate negative feedback. In this study, we tested how five different drugs, in addition to Dex and a saline control, affected the release of corticosterone (Cort) in house sparrows (Passer domesticus) that were restrained for 30 minutes. These additional drugs included methylprednisolone, fludrocortisone, isoflupredone, prednisolone, and hydrocortisone. Each drug was tested on 12 birds over the course of 6 weeks in a randomized order. Blood samples were taken after the initial 30-minute stressor, 45 minutes after injection, and 90 minutes after injection. All treatments, including saline, elicited a reduction in Cort release over the 90 minutes. Dex resulted in the strongest negative feedback, while hydrocortisone did not shut down the release of Cort; this is likely because hydrocortisone cross-reacts with the antibody in the radioimmunoassay used to quantify Cort. We hope that these results provide additional options for those whose study systems do not respond to Dex.
