EVIDENCE FOR SYMPATHETIC, PURINERGIC TRANSMISSION IN THE MESENTERIC-ARTERY OF THE DOG

Electrical transmural stimulation of isolated mesenteric artery of the dog produced a transient contraction 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 with .alpha.,.beta.-methylene-ATP (.alpha.,.beta.-MeATP). Desensitization induced by .alpha.,.beta.-MeATP 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 nonadrenergic contraction induced by electrical transmural stimulation is a sympathetic, purinergic response.