A re-appraisal of the mode of action of 5-HT in inhibiting GABA-induced cholinergic contractions in the guinea-pig ileum.
In the guinea-pig ileum, pretreatment with 5-hydroxytryptamine (5-HT) (5 microM) for 4-5 min inhibited both 5-HT- and gamma-aminobutyric acid (GABA)-induced cholinergic contractions without consistently altering those induced by electrical field stimulation. Cisapride (1 micron) antagonized 5-HT-induced cholinergic contractions but left those induced by GABA or twitch responses unchanged. These results indicate that the 5-HT action in inhibiting GABA-induced cholinergic responses may arise at the interneuronal level, thus suggesting that GABA may also indirectly activate cholinergic terminal neurons. These findings rule out the possibility of 5-HT acting as an intermediate transmitter in this type of response.
D000818:Animals; D002799:Cholinergic Fibers / Q000187:drug effects; D020117:Cisapride; D005260:Female; D018756:GABA Antagonists; D005769:Gastrointestinal Motility / Q000187:drug effects*; D006168:Guinea Pigs; D007082:Ileum / Q000187:drug effects* / Q000294:innervation; D066298:In Vitro Techniques; D008297:Male; D009130:Muscle, Smooth / Q000187:drug effects; D009451:Neuroeffector Junction / Q000187:drug effects; D010880:Piperidines / Q000494:pharmacology; D012701:Serotonin / Q000494:pharmacology*; D009435:Synaptic Transmission / Q000187:drug effects
D018756:GABA Antagonists; D010880:Piperidines; D012701:Serotonin; D020117:Cisapride