title: Investigation of the mechanism of nicotine-induced relaxation on the sheep sphincter of Oddi.
abstract: Possible mechanisms for nicotine-induced relaxation were investigated in the isolated sheep's sphincter of Oddi. Sheep's sphincter of Oddi rings were mounted in tissue bath with modified Krebs-Henseleit solution and aerated with 95% oxygen and 5% carbon dioxide. Tension was measured with isometric force transducers, and muscle relaxation was expressed as percent decrease of precontraction induced by carbachol. Nicotine (1 x 10(-5) to 3 x 10(-3) mol/L) produced concentration-dependent relaxation on sphincter of Oddi precontracted by carbachol (10(-6) mol/L). Nicotine-induced relaxation was 72.8 +/- 4.2% of precontraction with carbachol (10(-6) mol/L) (mean pD2 value, 3.76 +/- 0.05 mol/L). Nicotine-induced relaxation was not affected by N(w)-nitro L-arginine methyl ester (L-NAME) (3 x 10(-5) mol/L), methylene blue (10(-5) mol/L), indomethacin (10(-5) mol/L), hexamethonium (10(-5) mol/L), glibenclamide (10(-5) mol/L), 4-aminopyridine (10(-3) mol/L), tetraethylammonium (3 x 10(-4) mol/L), clotrimazole (10(-6) mol/L), 5-nitro-2-(3-phenylpropylamino) benzoic acid (NPPB) (10(-6) mol/L), and anthracene-9-carboxylate (9-AC) (10(-6) mol/L), but potentiated by bupivacain (10(-5) mol/L). A calcium-antagonizing effect of nicotine was not observed. The results suggest that nicotine-induced relaxation of the sheep's sphincter of Oddi is not mediated by the release of prostaglandins, nitric oxide (NO), or a related substance; by the activation of potassium channels or chloride channels; or by the stimulation of nicotinic cholinoceptors. Potentiation of the nicotine-induced relaxation by bupivacain indicates that blockade of sodium channels may play a role in this relaxation.
authors.affiliation: Department of Pharmacology, Cumhuriyet University School of Medicine, Sivas, Turkey.
authors.forename: Ihsan
authors.initials: I
authors.lastname: Bagcivan
authors.forename: Tijen
authors.initials: T
authors.lastname: Kaya
authors.forename: Mustafa
authors.initials: M
authors.lastname: Turan
authors.forename: Selçuk
authors.initials: S
authors.lastname: Goktas
authors.forename: Yeltekin
authors.initials: Y
authors.lastname: Demirel
authors.forename: Sinan
authors.initials: S
authors.lastname: Gursoy
mesh_terms: D000818:Animals; D004305:Dose-Response Relationship, Drug; D066298:In Vitro Techniques; D008297:Male; D009126:Muscle Relaxation / Q000187:drug effects* / Q000502:physiology; D009538:Nicotine / Q000494:pharmacology*; D012756:Sheep; D009803:Sphincter of Oddi / Q000187:drug effects* / Q000502:physiology
chemical_list: D009538:Nicotine