Study on sympathetic purinergic transmission in blood vessels

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Electrical transmural stimulatin of isolated mesenteric artery of the dog produced a transient contractin which consisted of adrenergic and non-adrenergic components. In contrast to the adrenergic component, the nonadrenergic component was resistant to prazosin and other adrenoceptor-blocking agents. However, the nonadrenergic component was completely blocked by guanethidine and by desensitization of P_2-purinoceptors with ,<beta>-methylene ATP. Desensitization of P_2-purinoceptors also inhibited the contractile response to ATP but not the adrenergic responses induced by electrical transmural stimulation and exogenous noradrenaline. These results suggest that the nonadrencergic contraction induced by electrical transmural stimulation is a sympathetic, purinergic response. Such purinergic responses were observed in the dog basilar and middle cerebral arteries andin the mesenteric, portal and saphenous veins, suggesting that the sympathetic purinergic transmission may paly a physiologically important role in the circulatory system.