Food Intake After an Overnight Fast is not Affected by Acute Alterations in Corticosterone but is Decreased by Chronic Adrenalectomy

Abstract

Corticosterone increases food intake in adrenalectomized rats and plasma corticosterone is 3-fold elevated in intact rats during an overnight fast, suggesting that the steroid may stimulate food intake in intact rats when food is provided. If so, this would present a challenge to maintenance of energy balance. Both chronic and acute effects of corticosterone were tested on feeding the next day after a 15 hour overnight fast in 5-day adrenalectomized rats. Similarly, RU486 was given acutely to intact rats. As expected, adrenalectomized rats replaced at surgery with corticosterone exhibited corticosterone dose-related increases in food intake and insulin levels during the first 8 hours after the fast. By contrast, treatment during the fast of: 1. intact rats with the glucocorticoid receptor antagonist RU486, 2. adrenalectomized steroid-replaced rats, with injections of corticosterone or 3. adrenalectomized rats with injections of corticosterone without prior steroid replacement, did not significantly affect food intake during the first 3–8 hours after the fast. Food intake did increase during 24 hours when previously untreated adrenalectomized rats were treated with corticosterone during the fast. In response to a stressor, acute corticosterone responses of similar magnitude occurred in intact rats both fed and fasted, but this did not affect their food intake during next 24 hours. We conclude that although chronic corticosterone treatment of adrenalectomized rats increases food intake, there is a prolonged lag between corticosterone treatment and increased food intake. Thus, acute corticosterone responses to stressors do not perturb the regulation of energy balance in intact animals; other mechanisms, such as elevated insulin secretion, intervene to blunt the chronic effects of corticosterone on food intake, and thus energy balance.