Effect of cisapride on the concentrations of beta-endorphinlike immunoreactivity and substance P-like immunoreactivity in the rat gastrointestinal tract.

Cisapride is a gastrointestinal prokinetic agent reported to be devoid of direct cholinergic effect from the myenteric plexus of the gut. The effect of cisapride (0.125, 0.5, 2mg/kg, i.p.) on the concentration beta-endorphin and substance P in rat gastrointestinal tract was studied. beta-Endorphinlike immunoreactivity contents were significantly increased in both mucosal and muscular layers of the entire gastrointestinal tract (from gastric body to rectum) of the rats treated with 2 mg/kg of cisapride. beta-Endorphinlike immunoreactivity contents were also increased in a part of the gastrointestinal tract of the rats treated with 0.125 or 0.5 mg/kg of cisapride. Substance P like immunoreactivity contents were significantly decreased in muscular layers of the rectosigmoid colon of the rats treated with 2 mg/kg of cisapride. This study suggests that the prokinetic effects of cisapride may relate to the contents of beta-endorphinlike immunoreactivity and substance P like immunoreactivity in gastrointestinal tract.