[Role of 5-HT3 receptors in the control by cholecystokinin of transient relaxations of the inferior esophageal sphincter in dogs].

Aims: The aim of this study was to determine, using specific antagonists, whether 5-HT3 receptors participate in triggering transient lower esophageal sphincter relaxations, independently or in relation with their CCKergic control.

Methods: Esophageal, lower esophageal sphincter and fundus pressure were manometrically monitored in 5 conscious dogs. Gastric distensions with air at constant pressure (1.0 and 1.7 kPa) were performed during 30 min under IV infusion of CCK8S (0.5 microgram/kg/h) or NaCl 9/1000 and were preceded (10 min) by IV administration of 5-HT3 receptors antagonists (ondansetron 0.2-500 micrograms/kg and granisetron 100 micrograms/kg) or NaCl 9/1000.

Results: The number of transient relaxations induced by a 1.7 kPa gastric distension (7.9 +/- 0.4/30 min) was dose-dependently reduced by ondansetron (1-100 micrograms/kg) and by granisetron (100 micrograms/kg). Ondansetron (100 micrograms/kg) did not modify the number of relaxations under a 1.0 kPa gastric pressure (2.7 +/- 0.4 vs 2.6 +/- 0.4/30 min) but reduced the increase of the occurrence of relaxations induced by CCK8S under a gastric pressure of 1.0 and 1.7 kPa.

Conclusion: These results suggest that the CCK control in triggering transient lower esophageal sphincter relaxations is modulated by serotonin via 5-HT3 receptors subtypes.