Functional evidence for a 5-HT2B receptor mediating contraction of longitudinal muscle in human small intestine.
Application of 5-hydroxytryptamine induces contraction of longitudinal muscle strips from human terminal ileum. The response was resistant to antagonism by ketanserin, ondansetron or DAU6285, but was non-surmountably antagonized by methysergide. The selective 5-HT2B/2C receptor antagonist, SB 200646A evoked a concentration-dependent, parallel and dextral displacement of the concentration-response curve to 5-HT, yielding a pA2 estimate of 7.17. Application of yohimbine, a 5-HT1 and 5-HT2B receptor antagonist, also induced a rightward shift of the response curve to 5-HT, yielding a pA2 estimate of 8.10. In conclusion, it appears that a 5-HT2B receptor mediates the contractile response of the longitudinal muscle of human small intestine to 5-HT.
Borman
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Department of Pharmacology, Queen Mary and Westfield College, London.
Burleigh
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D000109:Acetylcholine / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D006801:Humans; D007082:Ileum / Q000187:drug effects / Q000502:physiology; D007211:Indoles / Q000494:pharmacology; D007421:Intestine, Small / Q000187:drug effects* / Q000502:physiology; D008784:Methysergide / Q000494:pharmacology; D009119:Muscle Contraction / Q000187:drug effects* / Q000502:physiology; D011985:Receptors, Serotonin / Q000187:drug effects* / Q000502:physiology; D012701:Serotonin / Q000494:pharmacology*; D012702:Serotonin Antagonists / Q000494:pharmacology; D014508:Urea / Q000031:analogs & derivatives / Q000494:pharmacology; D015016:Yohimbine / Q000494:pharmacology
D007211:Indoles; D011985:Receptors, Serotonin; D012702:Serotonin Antagonists; C080864:N-(1-methyl-5-indolyl)-N'-(3-pyridyl)urea; D015016:Yohimbine; D012701:Serotonin; D014508:Urea; D000109:Acetylcholine; D008784:Methysergide