Gastric secretion and mucosal lesions in morphine-dependent rats.

The gastric mucosa and basal gastric secretion of morphine-dependent rats with pyloric occlusion were examined. Morphine tolerance and dependence were induced by administering increasing concentrations of morphine sulphate in the drinking water for 3 weeks, and were confirmed by a decreased analgesic response to morphine in the tail-immersion test and by occurrence of a naloxone-precipitated withdrawal syndrome, respectively. It was found that although the basal gastric secretion of morphine-dependent rats was not significantly different from that of naive animals, the former group showed a significantly higher gastric glandular mucosal ulcer index. Intraperitoneal injection of naloxone induced significant withdrawal effects but did not produce significant changes in gastric secretion or in ulcer index.