title: Effect of adenosine on adrenergic neurotransmission in the superfused rat portal vein.
abstract: This study examined the effect of exogenously applied adenosine on the release of 3H-norepinephrine from the field-stimulated, superfused rat portal vein. Adenosine was found to inhibit the field-stimulated release of 3H-norepinephrine in a dose-dependent manner in 50- to 1,000-microM concentrations. The effect was reversed when adenosine was washed out. The inhibitory effects of adenosine were antagonized by theophylline (10-4 M) which by itself showed a slight enhancement of stimulated 3H-norepinephrine release. ATP was found to inhibit 3H-norepinephrine release at the same concentration as adenosine while inosine was inactive. When adenosine was tested in the presence of the muscarinic and alpha-adrenergic blocking agents atropine and phenoxybenzamine along with indomethacin, a prostaglandin synthesis inhibitor, its inhibotory effect on the stimulated release of 3H-norepinephrine persisted. It is concluded that adenosine and/or ATP can modulate the nerve-stimulated induced release of norepinephrine presumably by an action on the adrenergic nerve terminals.
mesh_terms: D000241:Adenosine / Q000494:pharmacology*; D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D004558:Electric Stimulation; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000294:innervation* / Q000502:physiology; D009638:Norepinephrine / Q000378:metabolism*; D011169:Portal Vein / Q000294:innervation* / Q000502:physiology; D051381:Rats; D013564:Sympathetic Nervous System / Q000187:drug effects*; D009435:Synaptic Transmission / Q000187:drug effects*; D013806:Theophylline / Q000494:pharmacology
chemical_list: D000255:Adenosine Triphosphate; D013806:Theophylline; D000241:Adenosine; D009638:Norepinephrine