Atypical beta-adrenoceptor in vascular smooth muscle : studies on the sensitivity to bupranolol and the effects of sympathetic nerve denervation

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The present study was carried out to pharmacologically identify the subtype of beta-adrenoceptor that mediates relaxation of rat mesenteric artery, and to clarify the effects of chemical denervation of sympathetic nerve on beta-adrenoceptor functions, and the following new findings were obtained. 1) Beta-adrenoceptors that mediate relaxation of rat mesenteric artery are composed of two types : propranolol-sensitive and propranolol-insensitive beta-adrenoceptors. 2) Propranolol-sensitive beta-adrenoceptor is mainly beta-1 and propranolol-insensitive beta-adrenoceptor is beta-3. Beta-3 may have new pharmacological characteristics that are different from previous reports. 3) Chemical denervation of sympathetic nerves reduces the relaxant responses mediated through both beta-1 and beta-3.