title: Evidence for ATP as a cotransmitter in dog mesenteric artery.
abstract: Contractile responses of the dog mesenteric artery were obtained (after removal of endothelium) to transmural stimulation of the perivascular nerves and to exogenous application of ATP, noradrenaline, dopamine, 5-hydroxy-tryptamine and high potassium solution. The alpha-adrenoceptor antagonists prazosin and phentolamine preferentially reduced the response to noradrenaline and the secondary phase of the biphasic contractile response to nerve stimulation, whilst the addition of alpha, beta-methylene-ATP, which selectively desensitizes P2-purinoceptors, reduced only the contractions to ATP and the portion of the nerve-mediated response which was resistant to the alpha-adrenoceptor antagonists. The responses to nerve stimulation were reduced by the selective P1-purinoceptor agonist 2-chloroadenosine, and its effect was reversed by the P1-purinoceptor antagonist 8-phenyltheophylline. These results suggest that in dog mesenteric artery part of the response to sympathetic nerve stimulation is mediated by ATP acting on P1-purinoceptors on the arterial smooth muscle, and that P1-purinoceptors on the sympathetic nerve terminal can inhibit release of the neurotransmitters.
mesh_terms: D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000494:pharmacology / Q000502:physiology*; D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000818:Animals; D004285:Dogs; D004558:Electric Stimulation; D066298:In Vitro Techniques; D008638:Mesenteric Arteries / Q000502:physiology; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000502:physiology*; D018377:Neurotransmitter Agents
chemical_list: D000317:Adrenergic alpha-Antagonists; D018377:Neurotransmitter Agents; D000255:Adenosine Triphosphate; C002630:alpha,beta-methyleneadenosine 5'-triphosphate