| Jpn J Pharmacol. 1979 Aug;29(4):605-22. |
| Pharmacological studies of lycorenine, an alkaloid of Lycoris radiata Herb.: Vasodepressor mechanism in rats.[Pubmed: 537276] |
Vasodepressor mechanism of Lycorenine (an alkaloid of Lycoris radiata Herb.) was investigated in anesthetized rats.
METHODS AND RESULTS:
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.
CONCLUSIONS:
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. |
| Jpn J Pharmacol. 1980 Oct;30(5):655-64. |
| Pharmacological studies of lycorenine, an alkaloid of Lycoris radiata Herb.: II. Effects of blood pressure in rats and dogs and the mechanism of tachyphylaxis to the vasodepressor action of lycorenine in rats.[Pubmed: 6110797] |
METHODS AND RESULTS:
Blood pressure responses to Lycorenine were investigated in rats and dogs. Lycorenine (10--40 mg/kg p.o.) produced a decrease in blood pressure in conscious rats which was greater in hypertensive rats than in normotensive rats. In conscious dogs, Lycorenine (5 or 10 mg/kg i.v.) produced rises in blood pressure and heart rate except for a few instances, while it produced a decrease in blood pressure in pentobarbital anesthetized dogs. Thus, there are species differences in cardiovascular effects of Lycorenine between conscious rats and dogs. The development of tachyphylaxis to the vasodepressor actions of Lycorenine and its related compounds was related to their alpha-adrenergic blocking activities at the time of the second injection in anesthetized rats. Desipramine which abolished or diminished the development of tachyphylaxis to the vasodepressor action of Lycorenine (5 or 7.5 mg/kg i.v.), shortened the duration of its vasodepressor action and reduced its alpha-adrenergic blocking action.
CONCLUSIONS:
These results indicate that the development of tachyphylaxis to the vasodepressor action of Lycorenine is ascribed to maintenance of its alpha-adrenergic blocking action. |
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