5-HYDROXYTRYPTAMINE 3-RECEPTOR ANTAGONIST MODULATES GALLBLADDER EMPTYING AND MOTILIN RELEASE INDUCED BY ERYTHROMYCIN

In the present study we evaluated the effect of ondansetron (formerly indicated as GR38032F), a potent and selective type-3 5-hydroxytryptam ine receptor antagonist, on erythromycin-induced gallbladder emptying and motilin release, as well as gallbladder emptying induced by a regu lar meal in healthy volunteers. Gallbladder emptying was evaluated by sonography. Ondansetron, at the dose of 0.05 mg/kg, significantly redu ced (P < 0.001 by ANOVA) the gallbladder emptying induced by 2 mg/kg/h r erythromycin, but did not increase basal gallbladder volume or inhib it gallbladder emptying induced by a regular meal. Ondansetron also in hibited the motilin release induced by erythromycin (P < 0.001, by ANO VA). These results suggest that serotoninergic mechanisms modulate the effects of erythromycin on the gastrointestinal tract. The exact site of action of ondansetron remains to be identified.