Decreased acid secretion and gastric lesion production by morphine in rats.

The effects of graded doses of morphine on gastric secretion were studied in conscious rats with pyloric occlusion. It was found that, at doses which significantly prolonged the reaction time in the tail-immersion test, morphine significantly decreased both the volume and total acid output of gastric secretion. It was also observed that morphine produced gastric mucosal lesions in a dose-dependent manner. Pretreatment with naloxone 4 mg/kg significantly alleviated the gastric effects of morphine 32 mg/kg. It is suggested that the depressant effects of morphine on gastric secretion and the ulcerogenicity of the narcotic result from its stimulant activity on opiate receptors.