Vasodepressor mechanism of
lycorenine (an
alkaloid of Lycoris radiata Herb.) was investigated in anesthetized rats.
Lycorenine (1--10 mg/kg i.v.) produced dose-related decreases in blood pressure and heart rate and tachyphylaxis developed with repeated
injections. In the blood-perfused rat hindquarters,
lycorenine (62.5--500 micrograms i.a.) produced dose-related decreases both in mean blood pressure and in perfusion pressure, and the
lycorenine-induced decrease in perfusion pressure was abolished by
phenoxybenzamine or
hexamethonium.
Lycorenine (more than 1 mg/kg i.v.) blocked the pressor response to sympathetic nerve stimulation, but failed to block the
tachycardia induced by sympathetic nerve stimulation.
Lycorenine (7.5 or 15 mg/kg i.v.) reduced the spontaneous splanchnic nerve activity.
Lycorenine when given intracerebroventricularly produced decreases in blood pressure and heart rate only in large doses (over 500 micrograms). The maximal
bradycardia induced by
lycorenine was abolished by bilateral
vagotomy. It is suggested that
lycorenine may produce a decrease in blood pressure as the result of alpha-
adrenergic blockade in conjunction with the reduction of the spontaneous sympathetic nerve activity, and produce
bradycardia by modifying vagal activity.