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5-H[T.sub.3] receptors participate in CCK-induced suppression of food intake by delaying gastric emptying. Am J Physiol Regul Integr Comp Physiol 287: R817-R823, 2004. First published June 10, 2004; 10.1152/ajpregu.00295.2004.--Serotonin type 3 (5-H[T.sub.3]) receptors have been shown to participate in the negative-feedback control of food intake. We previously reported that cholecystokinin (CCK)-induced suppression of food intake is partly mediated through 5-H[T.sub.3] receptors when rats were tested on a preferred liquid diet, but whether such an effect occurs when they are tested on a solid maintenance diet is unknown. In the present study, we examined the effects of ondansetron, a selective 5-H[T.sub.3] antagonist, on CCK-induced suppression of solid chow intake. Intraperitoneal administration of ondansetron significantly attenuated 30- and 60-min CCK-induced reduction of food intake, with suppression being completely reversed by 120 min. It is not known whether 5-H[T.sub.3] receptors directly mediate CCK-induced satiation or whether their participation depends on CCK acting as part of a feedback cascade to inhibit ongoing intake. Because CCK-induced inhibition of sham feeding does not depend on additive gastric/postgastric-feedback signals, we examined the ability of ondansetron to reverse CCK-induced satiation in sham-feeding rats. Ondansetron did not attenuate reduction of sham feeding by CCK, suggesting that ondansetron does not directly antagonize CCK-satiation signals. CCK suppresses real feeding through a delay in gastric emptying. Ondansetron could attenuate CCK-induced reduction of rood intake by reversing CCK-induced inhibition of gastric emptying. We found that blockade of 5-H[T.sub.3] receptors attenuates CCK-induced inhibition of gastric emptying of a solid meal, as well as saline and glucose loads. We conclude that 5-H[T.sub.3] receptors mediate CCK-induced satiation through indirect mechanisms as part of a feedback cascade involving inhibition of gastric emptying. ondansetron; serotonin; osmotic; glucose; satiety

Hayes, Matthew R., Rachael L. Moore, Samit M. Shah, and Mihai Covasa. 5-HT3 receptors participate in CCK-induced suppression of food intake by delaying gastric emptying. Am J Physiol Regul Integr Comp Physiol 287:R817-R823, 2004. First published June 10, 2004; 10.1152/ajpregu.00295.2004.—Serotonin type 3 (5-HT3) receptors have been shown to participate in the negative-feedback control of food intake. We previously reported that cholecystokinin (CCK)- induced suppression of food intake is partly mediated through 5-HT3 receptors when rats were tested on a preferred liquid diet, but whether such an effect occurs when they are tested on a solid maintenance diet is unknown. In the present study, we examined the effects of ondansetron, a selective 5-HT3 antagonist, on CCK-induced suppression of solid chow intake. Intraperitoneal administration of ondansetron significantly attenuated 30- and 60-min CCK-induced reduction of food intake, with suppression being completely reversed by 120 min. It is not known whether 5-HT3 receptors directly mediate CCK-induced satiation or whether their participation depends on CCK acting as part of a feedback cascade to inhibit ongoing intake. Because CCK- induced inhibition of sham feeding does not depend on additive gastric/postgastric-feedback signals, we examined the ability of ondansetron to reverse CCK-induced satiation in sham-feeding rats. Ondansetron did not attenuate reduction of sham feeding by CCK, suggesting that ondansetron does not directly antagonize CCK-satiation signals. CCK suppresses real feeding through a delay in gastric emptying. Ondansetron could attenuate CCK-induced reduction of food intake by reversing CCK-induced inhibition of gastric emptying. We found that blockade of 5-HT3 receptors attenuates CCK-induced inhibition of gastric emptying of a solid meal, as well as saline and glucose loads. We conclude that 5-HT3 receptors mediate CCK- induced satiation through indirect mechanisms as part of a feedback cascade involving inhibition of gastric emptying. [ABSTRACT FROM AUTHOR]