CENTRALLY ADMINISTERED NEUROPEPTIDE-Y (NPY) INHIBITS GASTRIC-EMPTYINGAND INTESTINAL TRANSIT IN THE RAT

Neuropeptide Y is distributed abundantly not only in the brain, but al so in the gastrointestinal tract and suppresses intestinal muscle cont raction in isolated muscle preparations. The purpose of the present st udy was to determine whether centrally administered neuropeptide Y mod ulated gastric emptying and intestinal transit in conscious rats. Grad ed doses of neuropeptide Y were administered intracisternally 1 min be fore ingestion of test meals through an oral tube. Four hours after in gestion of 60 Amberlite pellets, the rats were sacrificed and residual pellets in the stomach and the small intestine segments were counted to calculate the solid meal transit rate. The liquid meal transit rate was calculated 1 hr after 0.07% phenol red ingestion by determining t he residual phenol red in the stomach and the small intestine segments . Neuropeptide Y elicited potent suppression of gastric emptying and i ntestinal transit of both solid and liquid meals. Pretreatment with pr opranolol antagonized, whereas phentolamine did not affect, the suppre ssive effect of central neuropeptide Y. Although carbachol blocked the effects of neuropeptide Y, neither atropine nor hexamethonium altered the actions of neuropeptide Y. In conclusion, centrally administered neuropeptide Y strongly inhibited gastrointestinal transit by stimulat ing a beta-adrenergic pathway.