Inhibitory action of 5-hydroxytryptamine on propulsive activity of the guinea-pig isolated colon.
The effects of 5-hydroxytryptamine (5-HT) and its receptor subtype agonists on spontaneous propulsive activities of the segment, and on changes in tension of the muscle strips were examined in the guinea-pig isolated distal colon. 5-HT, 5-carboxamidotryptamine (5-CT), alpha-methyl-5-HT and t-methoxytryptamine (5-MeOH), applied to the serosal side of the segment, inhibited spontaneous propulsive activities, but 2-methyl-5-HT did not. On the indomethacin-treated segment, 5-HT and its receptor subtype agonists all stimulated propulsive activity. 5-HT, 5-CT, alpha-methyl-5-HT and 5-MeOH relaxed circular muscle strips, which were inhibited in the presence of tetrodotoxin. However, these agonists showed contractile effects on the indomethacin-treated circular muscle strips. These results suggest that 5-HT may inhibit spontaneous propulsive activities of the colonic segment via release of endogenous PGs (e.g., E and I types) in the circular muscle cells mediated by an inhibitory neurotransmitter, which release was stimulated by 5-HT1-like 5-HT2 and 5-HT4 receptors on the myenteric neurones in the circular muscle layer.
Ishizawa
M
M
Laboratory of Physiology, School of Health Sciences, Sapporo Medical University, Japan.
D008735:5-Methoxytryptamine / Q000494:pharmacology; D000818:Animals; D003106:Colon / Q000187:drug effects* / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D006168:Guinea Pigs; D066298:In Vitro Techniques; D007211:Indoles / Q000494:pharmacology; D007213:Indomethacin / Q000494:pharmacology; D007650:Ketanserin / Q000494:pharmacology; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects*; D012701:Serotonin / Q000031:analogs & derivatives / Q000494:pharmacology*; D012702:Serotonin Antagonists / Q000494:pharmacology*; D017366:Serotonin Receptor Agonists / Q000494:pharmacology*; D013779:Tetrodotoxin / Q000494:pharmacology; D000077526:Tropisetron
D007211:Indoles; D012702:Serotonin Antagonists; D017366:Serotonin Receptor Agonists; C042390:alpha-methylserotonin; D012701:Serotonin; D008735:5-Methoxytryptamine; D013779:Tetrodotoxin; D000077526:Tropisetron; C045918:2-methyl-5-HT; D007650:Ketanserin; D007213:Indomethacin