ABSTRACT
Dihydrolycorine(DL)HCI was produced semisynthetically from lycorine which is an alkaloid isolated from lycoris radiata Herb.The dose-response curves for phenylephrine iv to increase mean arterial pressure were shifted rightward by DL 40 mg/kg iv in anesthetized cats.The dose- response curves for phenylephrine iv to increase diastolic pressure were shift- ed rightward by DL iv in pithed rats:but DL didn't shift the dose-response curves of BHT_(920).In rat anococcygeal muscle,DL 3,10,30,100uM/L shifted cumulative dose-response curves of methoxamine rightward parallelly with pa2 value 6.35.In the isolated rabbit aortic ring,DL 10,30,100uM/L also shifted cumulative dose-response curves of methoxamine rightward parallelly with pA2 value 5.93.These results suggest that DL can block a-adrenoceptors.