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


CONCLUSIONS
These results suggest that the CCK control in triggering transient lower esophageal sphincter relaxations is modulated by serotonin via 5-HT3 receptors subtypes.
Rouzade
M L
ML
Laboratoire de Pharmacologie-Toxicologie, INRA, Toulouse.
Fioramonti
J
J
Bueno
L
L
D000818:Animals; D002766:Cholecystokinin / Q000502:physiology*; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D004943:Esophagogastric Junction / Q000502:physiology*; D017829:Granisetron / Q000494:pharmacology; D008297:Male; D008365:Manometry; D009126:Muscle Relaxation / Q000502:physiology*; D017294:Ondansetron / Q000494:pharmacology; D011985:Receptors, Serotonin / Q000502:physiology*; D044406:Receptors, Serotonin, 5-HT3; D012702:Serotonin Antagonists / Q000494:pharmacology
D002766:Cholecystokinin; D017829:Granisetron; D017294:Ondansetron; D011985:Receptors, Serotonin; D044406:Receptors, Serotonin, 5-HT3; D012702:Serotonin Antagonists