[Effect of epiberberine on alpha-adrenoceptors]

In rats vas deferens and canine saphenous vein, epiberberine (EB) parallelly shifted the dose-response curves of Clo and BHT-920 to the right without changing the maximal effect. The pA2 values of EB were found to be 6.5 and 6.8 respectively. EB was shown to competitively antagonize the contractile response of isolated rabbit aortic strips and canine saphenous vein strips to Meth with pA2 values of 5.8 and 6.4 respectively. EB given intravenously to anesthetized rats was shown to decrease blood pressure temporarily and accelerate heart rate gradually. The heart rate was increased persistently and constantly in spite of blood pressure restoration. The results suggest that EB possesses poor alpha-blocking action.