Effect of erythromycin on different parts of the rabbit intestine: comparison with motilin.

1. The effect of erythromycin on the rabbit intestinal smooth muscle was investigated and was compared to that of motilin. 2. Whole isolated segments from the duodenum, jejunum, ileum and ascending colon, as well as strips from the circular and longitudinal smooth muscle of the ascending colon were used. 3. Erythromycin was found to possess a concentration-dependent contractile effect on the above intestinal parts but in different degree of intensity. 4. The order of the sensitivity of the intestinal parts to erythromycin was duodenum = jejunum > ascending colon > ileum. 5. The circular smooth muscle of the ascending colon was found to be more sensitive than the longitudinal smooth muscle. 6. A similar contractile effect, but at lower concentrations, and the same regional specificity were observed with motilin.