|
Plantaginis seed has been applied in Chinese medicine as well as in folk remedy. It was advocated that Plantaginis Semen exerts good therapeutic effects as anti-inflammatory, antitussive, obstipant and diuretic agent in some cases of alimentary, respiratory and renal disorders. This study was carried out in order to re-evaluate the pharmacological action, especially the hypotensive action of Plantaginis Semen and to elucidate the mechanism of its action, making use of Plantaginis Semen methanol extract (PME), because its basic pharmacological action, i.e., hypotensive action is not clear. 1) PME, when administered into intravenous route, elicited the hypotensive response dependent on the dose of PME given to the rabbit anesthetized with urethane. 2) This hypotensive response of PME was inhibited by atropine and potentiated by physostigmine, but not influenced by vagotomization. 3) Depressor effect of PME was blocked by chlorisondamine, phentolamine, and bethanidine, while not altered by cyproheptadine, diphenhydramine and propranolol. 4) The secondary pressor response after blocking the depressor effect of PME by chlorisondamine was produced, but this pressor response was deminished by atropine. 5) PME augmented the pressor effect of norepinephrine and angiotensin, on the other hand, reduced blood pressure elevated by carotid occlusion reflex. 6) These observations suggest that PME may induce the hypotensive response via dual mechanisms of parasympathomimetic and sympatholytic action, that the positions of this action are cholinergic peripheral site and sympathetic ganglia respectively, and that PME may possess the pressor activity caused by stimulation of "atropine-sensitive site" which seems to existsin the sympathetic ganglia.
|