The effect of some centrally active drugs on corticosterone secretion and metabolism in rats.

1. Male rats were treated with morphine sulphate (10 mg/kg), methadone (10 mg/kg) and chlorpromazine (8.0 mg/kg) respectively, for 2 weeks. 2. At the end of this period, the adrenal glands of treated rats had increased in weight. 3. The concentration of corticosterone in the peripheral plasma was significantly lowered in the chlorpromazine-treated rats, increased in the methadone-treated rats and was unchanged in the morphine-treated rats. 4. The metabolic clearance rate of [1,2-3H]corticosterone decreased in the chlorpromazine-treated rats, while only a slight reduction was observed with methadone treatment. 5. These results showed that chronic treatment with either morphine or methadone did not suppress the adrenal function. The possible site of action of chlorpromazine in suppressing corticosterone secretion is discussed.