EVIDENCE FOR TWO DISTINCT TYPES OF POSTSYNAPTIC α‐ADRENOCEPTOR IN VASCULAR SMOOTH MUSCLE in vivo

摘要: 1 The effects of the highly selective alpha(1)-adrenoceptor antagonist, prazosin, and relatively alpha(2)-adrenoceptor yohimbine, on pressor responses to intravenous injections phenylephrine noradrenaline have been examined in anaesthetized cats pithed rats an attempt determine whether alpha(1)- alpha(2)-adrenoceptors are located postsynaptically vascular smooth muscle.2 In prazosin caused a much greater reduction than or splanchnic nerve stimulation (after adrenalectomy). Yohimbine was similar potency reducing each stimulus.3 A differential blocking activity against intra-arterial also demonstrated blood-perfused cat hind limb. As whole animal, more potent noradrenaline. similar, though less marked, effect seen mesenteric circulation, but not renal where almost equipotent noradrenaline.4 potent, competitive antagonist phenylephrine, had little noradrenaline; only high doses were reduced by prazosin. approximately as anococcygeus muscle, it muscle.5 results suggest that there two types alpha-adrenoceptor vasculature rats. Phenylephrine produces stimulating one type postsynaptic is blocked yohimbine; these alpha(1)-adrenoceptors. Noradrenaline exerts some its via receptors most appears be exerted through prazosin-insensitive receptors. latter appear differ from alpha(2)-adrenoceptors.