title: Mechanism of rhythmic contractions induced by uranyl ion in the ileal longitudinal muscle of guinea-pig.
abstract: The uranyl ion (UO2(2+)) produces rhythmic contractions of the longitudinal muscle of the ileum, similar to those induced by repetitive transmural stimulation. Hexamethonium inhibited the action of UO2(2+), indicating a preganglionic site of action of UO2(2+) and interneurons possibly being involved in the ACh-releasing effect of UO2(2+). In addition, the action of UO2(2+) was enhanced by physostigmine but antagonized by atropine, ATP, adrenaline and morphine suggesting multiple sites of action of UO2(2+). The effects of Ba2+ were studied simultaneously in order to compare them with those of UO2(2+). Atropine and hexamethonium had no effect on the rhythmic contractions with Ba2+ but physostigmine enhanced contractions induced by low concentration of Ba2+ indicating that Ba2+ induces contractions mainly by acting on the smooth muscle and releases ACh from the nerve to a lesser extent.
authors.forename: W M
authors.initials: WM
authors.lastname: Fu
authors.forename: S Y
authors.initials: SY
authors.lastname: Lin-Shiau
mesh_terms: D000109:Acetylcholine / Q000378:metabolism; D000818:Animals; D001464:Barium / Q000494:pharmacology; D005260:Female; D006168:Guinea Pigs; D018738:Hexamethonium; D006584:Hexamethonium Compounds / Q000494:pharmacology; D007082:Ileum / Q000187:drug effects*; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects*; D010830:Physostigmine / Q000494:pharmacology; D014501:Uranium / Q000494:pharmacology*
chemical_list: D006584:Hexamethonium Compounds; D001464:Barium; D018738:Hexamethonium; D014501:Uranium; D010830:Physostigmine; D000109:Acetylcholine