Participation by purines in the modulation of norepinephrine release by methoxamine.
The alpha 1-receptor agonist methoxamine reduced, by a prazosin sensitive mechanism, the nerve stimulation evoked release of norepinephrine in the rat caudal artery. The effect of methoxamine was also antagonized by the purinoceptor antagonist 8-(p-sulfophenyl)theophylline suggesting an involvement of endogenous purines in this process. Indeed, methoxamine caused the release of adenine nucleotides and adenosine, an action which was blocked by prazosin. These results suggest that methoxamine releases ATP or a related purine which in turn decreases transmitter release by acting on prejunctional purinoceptors.
Shinozuka
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Department of Pharmacology, University of Nevada School of Medicine, Reno 89557.
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D000227:Adenine Nucleotides / Q000378:metabolism; D000241:Adenosine / Q000378:metabolism; D000818:Animals; D004558:Electric Stimulation; D066298:In Vitro Techniques; D008297:Male; D008729:Methoxamine / Q000494:pharmacology*; D009638:Norepinephrine / Q000378:metabolism*; D011224:Prazosin / Q000494:pharmacology; D051381:Rats; D011916:Rats, Inbred F344; D011983:Receptors, Purinergic / Q000502:physiology*
D000227:Adenine Nucleotides; D011983:Receptors, Purinergic; D008729:Methoxamine; D000241:Adenosine; D009638:Norepinephrine; D011224:Prazosin