title: Evidence that adenosine is not involved in the non-adrenergic non-cholinergic relaxation in the rat duodenum.
abstract: In rat isolated duodenal segments, adenosine induced, in the presence of atropine and guanethidine, a dose-dependent, long-lasting (about 20 s), tetrodotoxin (TTX)-resistant relaxation both in endoluminal pressure and in isometric tension. Electrical field stimulation (EFS) induced, in the presence of atropine and guanethidine, a TTX-sensitive short-lasting (about 6 s) relaxation followed by a sustained rebound contraction. Theophylline, a P1 receptor antagonist, at the concentration of 100 microM caused a marked inhibition of the adenosine-induced relaxation, while the EFS-induced relaxation was not modified. Our results suggest that adenosine induces relaxation of the rat duodenal smooth muscle acting on P1 receptors localized at muscular level. However, differences in the morphology and in the sensitivity to theophylline between adenosine- and EFS-induced relaxation ruled out adenosine as neurotransmitter of the non-adrenergic, non-cholinergic inhibitory system.
authors.affiliation: Dipartimento di Biologia cellulare e dello Sviluppo, Università di Palermo, Italia.
authors.forename: F
authors.initials: F
authors.lastname: Mulè
authors.forename: R
authors.initials: R
authors.lastname: Serio
authors.forename: A
authors.initials: A
authors.lastname: Postorino
mesh_terms: D000241:Adenosine / Q000037:antagonists & inhibitors / Q000502:physiology*; D000818:Animals; D001285:Atropine / Q000494:pharmacology; D004386:Duodenum / Q000187:drug effects / Q000294:innervation*; D004558:Electric Stimulation; D006145:Guanethidine / Q000494:pharmacology; D066298:In Vitro Techniques; D007537:Isometric Contraction / Q000187:drug effects; D009126:Muscle Relaxation / Q000187:drug effects / Q000502:physiology; D009130:Muscle, Smooth / Q000187:drug effects / Q000294:innervation*; D011312:Pressure; D051381:Rats; D011983:Receptors, Purinergic / Q000187:drug effects; D013779:Tetrodotoxin / Q000494:pharmacology; D013806:Theophylline / Q000494:pharmacology
chemical_list: D011983:Receptors, Purinergic; D013779:Tetrodotoxin; D001285:Atropine; D013806:Theophylline; D000241:Adenosine; D006145:Guanethidine