THE ACTION OF BENZYLTETRAHYDROPALMATINE ON ? ADRENOCEPTOR / 中国药理学通报

ABSTRACT

The action of BTHP on a-adrenoceptor was studied in anococcy-geus muscles, vas deferens and cell membrane of cerebral cortex of rats and aortic strips, saphenous vein of rabbit. BTHP produced parallel shifts to the right of dose-response curves for phenylephrine in rat anococcygeus muscle and rabbit aortic strips without change in the maximal responses. Their pA2 values were 5.8 and 5.86 respectively. BTHP was also a competitive antagonist for presynaptic and postsynaptic ?2-adrenoceptors on prostatic portion of rat vas deferens( pA2 against clonidine=5.2 ) and on rabbit saphenous vein ( pA2 against B-HT920=5.3 ) . BTHP decreased in dose-dependent manner 〔8H〕 prazosin and 〔3H〕 clonidine specific binding to ?1- and ?2- adrenoceptors on cell membrane of cerebral cortex in rats with IC50 of4 and 9.5 ?mol/L and with Ki ( apparent dissociation constant ) of 3.5 and 8.1?mol/L respectively, suggeating that BTHP has affinity for both ?1 and ?2- adrenoceptors of rat cerebrance.