SEROTONIN AND CHOLECYSTOKININ ACTIVATE DIFFERENT POPULATIONS OF RAT MESENTERIC VAGAL AFFERENTS

This electrophysiological study was performed to elucidate the interac tions of serotonin (5-hydroxytryptamine, 5-HT) and cholecystokinin (CC K) on mesenteric afferents supplying the rat jejunum. 5-HT and CCK pro duced characteristic responses in multi-unit recordings of mesenteric afferents. Waveform analysis to extract single units from the whole ne rve recording identified populations of single afferents that were sen sitive to either 5-HT or CCK, but not both. Furthermore, devazepide (0 .5 mg/kg) completely abolished the response to CCK without altering th e response to 5-HT while granisetron (0.5 mg/kg) abolished the respons e to 5-HT with no effect on the response to CCK. These results suggest that there are discrete, noninteractive populations of jejunal affere nts that possess either 5-HT3 or CCK-A receptors but not both. (C) 199 8 Published by Elsevier Science Ireland Ltd. AIl rights reserved.