Autonomic nervous system mediates the cardiovascular effects of Rhodiola sacra radix in rats.
BACKGROUND
Rhodiola sacra (Crassulaceae) exhibits cardiovascular bioactivities and is used in Tibetan medicine for promoting circulation and preventing hypertension. However, the underlying mechanisms of its cardiovascular effects are poorly understood.


OBJECTIVE
The aim of this study was therefore to evaluate the cardiovascular activity of water-soluble fraction (WtF) and n-butanol-soluble fraction (BtF) of Rhodiola sacra radix and to explore its mechanism of action in propofol anesthetized Sprague-Dawley rats.


METHODS
The changes of blood pressure, heart rate and cardiac contractility after systemic administration of the extracts (10-75 mg/kg) were examined for at least 40 min. Different antagonists were used to evaluate the mechanisms of cardiovascular effects of the extracts.


RESULTS
Intravenous injection of the WtF (10, 25, 35, 50 or 75 mg/kg) exhibited dose-dependent hypotension and increases in heart rate and cardiac contractility. In contrast, mild alterations in the same cardiovascular parameters were detected only at high dose (75 mg/kg) BtF. The WtF-induced hypotensive, positive inotropic and chronotropic effects were significantly abolished by pretreatment with hexamethonium (30 mg/kg, i.v.) or reserpine (5 mg/kg, i.v.), whereas the hypotensive, but not the positive inotropic or chronotropic effect was potentiated by captopril (2.5 mg/kg, i.v.). Pretreatment with methylatropine (1 mg/kg, i.v.), on the other hand, reversed the positive inotropic and chronotropic but not the hypotensive effects of WtF. The WtF-induced cardiovascular responses were not affected in rats pretreated with N(G)-nitro-l-arginine methyl ester (20 mg/kg, i.v.).


CONCLUSIONS
We conclude that systemic administration of the WtF of Rhodiola sacra radix elicited a potent hypotensive effect that was mediated by the withdrawal of sympathetic vasomotor tone and interaction with the circulatory angiotensin system. The positive inotropic and chronotropic effects of WtF may result from a direct vagal inhibition on the heart.
Shih
Cheng-Dean
CD
Department of Pharmacy and Graduate Institute of Pharmaceutical Technology, Tajen University, 20 Weishin Road, Yanpu Township, Pingtung County 90741, Taiwan. cdshih@mail.tajen.edu.tw
Kuo
Daih-Huang
DH
Huang
Chi-Wen
CW
Gu
Yu-Hua
YH
Chen
Fu-An
FA
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects*; D002316:Cardiotonic Agents / Q000008:administration & dosage / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D006339:Heart Rate / Q000187:drug effects; D007275:Injections, Intravenous; D008297:Male; D038861:Medicine, Tibetan Traditional; D009200:Myocardial Contraction / Q000187:drug effects*; D010936:Plant Extracts / Q000008:administration & dosage / Q000494:pharmacology*; D018517:Plant Roots; D051381:Rats; D017207:Rats, Sprague-Dawley; D012084:Renin-Angiotensin System / Q000187:drug effects; D029771:Rhodiola / Q000737:chemistry*; D014630:Vagus Nerve / Q000187:drug effects / Q000378:metabolism; D014666:Vasomotor System / Q000187:drug effects / Q000378:metabolism
D002316:Cardiotonic Agents; D010936:Plant Extracts