title: Substance P mediates atropine-sensitive response of guinea-pig ileum to serotonin.
abstract: The action of serotonin (5HT) was investigated on guinea-pig isolated ileum. Low concentrations of 5HT (10(-8) - 2.5 x 10(-7) mol x 1(-1)) produced contractile responses which were abolished by atropine and by methionine enkephalin but not by methysergide. Higher concentrations of 5HT (5 x 10(-7) - 5 x 10(-6) mol x 1(-1)) produced contractions which were inhibited by methysergide. The atropine-sensitive response was also abolished following desensitization of preparations to substance P and by the substance P antagonist [D-Pro2,D-Phe7,D-Trp9]SP. It was concluded that the atropine-sensitive response to 5HT is mediated by substance P.
mesh_terms: D000818:Animals; D001285:Atropine / Q000494:pharmacology*; D002211:Capsaicin / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005260:Female; D006168:Guinea Pigs; D007082:Ileum / Q000187:drug effects*; D066298:In Vitro Techniques; D008297:Male; D009538:Nicotine / Q000494:pharmacology; D012701:Serotonin / Q000494:pharmacology*; D013373:Substance P / Q000378:metabolism / Q000494:pharmacology*
chemical_list: D012701:Serotonin; D013373:Substance P; D009538:Nicotine; D001285:Atropine; D002211:Capsaicin