The effects of granisetron, ICS 205–930 and ondansetron on the visceral pain reflex induced by duodenal distension

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Abstract
1 Distension of the duodenum in anaesthetized rats, by rapid application of intraluminal pressures (10–75 cmH2O), evoked falls in diastolic blood pressure and intragastric pressure. 2 The distension-induced responses were blocked by pretreatment with morphine (20 mg kg−1, s.c.), an action reversible by injection of naloxone (5 mg kg−1, i.v.). 3 Bilateral cervical vagotomy reduced the distension-evoked fall in intragastric pressure but had no effect on the corresponding fall in blood pressure. 4 Granisetron or ICS 205–930 (1–1000 μg kg−1, i.v.) had no effects on duodenal intraluminal pressure, but reduced the responses to distension with a bell-shaped dose-response relationship. Ondansetron (1–1000 μg kg−1, i.v.) did not reduce the reflex responses. 5 These results show that the 5-HT3 receptor antagonists used exerted different effects on the reflex responses to duodenal distension.