Adrenal, plasma and urinary corticosteroids during single or repeated administration of morphine in cats

Corticosteroids and ascorbic acid in the adrenal glands of adult cats have been investigated after single or repeated administration of morphine. Also plasma levels and urinary excretion of corticosteroids were determined. A significant increase in the content of corticosteroids in the glands and plasma was found after initial injection of morphine. After 7 days of consecutive morphine treatment a fall of corticosteroids in the glands was observed; after 2 weeks of daily injections the content of adrenal corticosteroids was significantly lower than in the control animals but no change was found in the plasma. Administration of the drug during 1 month led to a highly significant decrease of corticosteroids in the glands as well as in plasma. No significant change in adrenal ascorbic acids was found whether the adrenal corticosteroids were higher or lower than in the control cats. Urinary corticosteroids were high during the first week of morphine treatment but thereafter the excretion declined progressively and was lower than the control level after 13 days of treatment. The significant decrease of corticosteroids observed after repeated administration of morphine and the rise in adrenal corticosteroids found after the injection of nalorphine to the morphinized animals suggest that some kind of morphine dependence had been developed in the cats after repeated administration of the drug.