EFFECT OF INTRAGASTRIC ADMINISTRATION OF BETA-ENDORPHIN ON THYROTROPIN-RELEASING-HORMONE AND SOMATOSTATIN RELEASE INTO GASTRIC LUMEN OF RATS

The neuropeptides beta-endorphin (BE), thyrotropin-releasing hormone ( TRH), and somatostatin (SOM) in the gastric mucosa have the capacity t o regulate gastric function. To clarify the possible role of BE in the interactions of neuropeptides and gastric acid secretion we investiga ted the effect of the intragastric administration of BE on TRH and SOM release into the gastric lumen. BE (100 ng/kg) induced an immediate d ecrease in TRH release and a reciprocal increase in SOM release into t he gastric lumen, followed by the suppression of gastric acid secretio n. When various doses of BE (0-500 ng/kg) were administered, changes i n TRH and SOM occurred in a dose-dependent manner. Pretreatment with n aloxone dihydrochloride (5 mg/kg, intraperitoneally) completely inhibi ted the BE-induced changes in the release of these peptides. These fin dings suggest that BE has a paracrine effect on TRH and SOM release in to the gastric lumen through opioid receptors, and that these interact ions may be involved in the regulation of gastric acid secretion.