EFFECTS OF OPIATE RECEPTOR AGONISTS AND ANTAGONISTS ON THE STRESS-INDUCED SECRETION OF CORTICOSTERONE IN MICE

Intraperitoneal administration of normorphine, morphine or naloxone or exposure to ethervapour for 1 miri, elevated plasma corticosteroid concentrations in mice. Injection of saline or exposure to ether vapour rendered mice less sensitive to a subsequent exposure to ether vapour 15 min later. Treatment with normorphine (50 mg/kg) potentiated the corticosteroid response to ether stress whilst pentazocine (20 mg/kg), naltrexone (10 mg/kg), morphine (24 mg/kg), levorphanol (20 mg/kg) and naloxone (50 mg/kg) prevented the stress‐induced elevation of plasma corticosteroids. Both naloxone and morphine inhibited the potentiation by normorphine of the response to ether, the dose of naloxone required being higher than that for inhibition of normorphine analgesia. It is concluded that endogenous opioid peptides may be involved in the control of the response to ether stress in mice. 1979 British Pharmacological Society