Study of the mechanism underlying the prokinetic action of erythromycin on lower esophageal sphincter pressure in dogs

Erythromycin [EM] and a number of its derivatives exhibit prokinetic properties. In particular, the drug increases the contractile activity of smooth muscles of esophagus and promotes gastric emptying in both health and disease. The drug enhances esophageal and gastric motility by acting as a motilin agonist. The aim of the study was to evaluate the effect of low dose of EM, as a prokinetic agent, on the lower esophageal sphincter pressure [LESP] and to study the receptors involved in the mediation of the prokinetic action of EM. The study was carried out on 30 adult healthy dogs [10-15 kg] divided into five groups, each group consisted of 6 dogs. The studied groups were: I: a control group [placebo treated], II: an erythromycin treated group [EM gp] [7 mg/kg b.w. by i.v.i], and three groups III, IV, V that were treated with EM [7 mg/kg b.w. i.v.L preceded by either atropine [a muscarinic blocker] in a dose of 40 micro ag/kg b.w. i.v.i., ondansetrone [5 HT3 antagonist] in a dose of 0.1 mg/kg b.w. i.v.i or metoclopramide [dopamine receptor type 2 antagonist] in a dose of 150 micro g/kg b.w. i.v.i. respectively. After an over night fasting, basal recording of LESP was carried out in each group by an esophageal manometer connected to a pressure transducer. LESP was recorded for all animals in all groups fifteen minutes after the end of the predescribed treatments. Data obtained showed that EM significantly increased the resting LESP. Pretreatment with either atropine or ondansetrone totally prevented the increase in LESP induced by EM. However, pretreatment with metoclopramide failed to prevent the increase in LESP induced by EM. The findings suggest that EM in a low, subantimicrobial dose has a prokinetic action on the lower esophageal sphincter. It was found that this prokinetic action is exerted most probably by stimulating cholinergic pathway and strongly suggested that 5 HT3 receptors are involved in this process. Meanwhile, the dopaminergic receptors seem to have no role in the mediation of this prokinetic action of EM. It is hoped that this prokinetic action of EM could be of a particular benefit in the improvement of GIT motility disorders. However this warrants further investigation to help more understanding of cellular mechanisms regarding that effect of EM