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Chronic stress alters brain and peripheral glucocorticoid and mineralocorticoid receptors in a wild bird

Although sustained high glucocorticoid titers can result in pathology, the effects of chronic stress on peripheral tissue sensitivity to glucocorticoids are not well understood. In this study, we subjected house sparrows (n=24) to a 3‐week standardized chronic stress protocol followed by a week of recovery and compared their glucocorticoid and mineralocorticoid receptor binding to that of control birds (n=18). We examined receptors in 9 tissues: whole brain, liver, muscle, fat, kidney, spleen, skin, testes and ovary. Animals were sacrificed weekly in the stress group, and every other week in the control group. Unlike previous work, which has typically demonstrated decreased tissue sensitivity in response to sustained high glucocorticoid titers, we found that chronic stress either did not affect receptor binding (skin, fat, liver and spleen) or increased receptor binding in a time‐and tissue‐dependent manner (muscle, brain, kidney, ovary and testes). Most chronic‐stress induced effects disappeared after a week of recovery, but receptor binding in pectoralis muscle remained high, suggesting ongoing metabolic disruption. Work supported by NSF, EPA, and Tufts University.