title: Mechanisms of the relaxant effect of a danshen and gegen formulation on rat isolated cerebral basilar artery.
abstract: OBJECTIVE
  Danshen (root of Salvia miltiorrhiza) and gegen (root of Pueraria lobata) are two herbs used in traditional Chinese medicine, most commonly for their putative cardioprotective and anti-atherosclerotic effects. In this study, the actions of a danshen and gegen formulation (DG; ratio 7:3) were investigated on rat-isolated cerebral basilar artery.
  
  
  METHODS
  Rat basilar artery rings were precontracted with 100 nM U46619. Involvement of endothelium-dependent mechanisms was investigated by mechanical removal of the endothelium; K(+) channels were investigated by pretreatment of the artery rings with various K(+) channel inhibitors, and Ca(2+) channels were investigated in artery rings incubated with Ca(2+)-free buffer and primed with 100 nM U46619 for 5 min prior to adding CaCl(2) to elicit contraction.
  
  
  RESULTS
  DG produced concentration-dependent relaxation of the artery rings with an IC(50) of 895±121 μg/ml. Mechanical removal of the endothelium or pretreatment with the BK(Ca) channel inhibitor iberiotoxin (100 nM), the K(V) channel inhibitor 4-aminopyridine (1 mM), or the K(IR) channel inhibitor barium chloride (100 μM), all had no effect on the DG-induced response (P>0.05 for all). However, pretreatment with the K(ATP) channel inhibitor glibenclamide (1 μM), the non-selective K(+) channel inhibitor tetraethylammonium (TEA, 100 mM), or a combination of all the K(+) channel inhibitors (iberiotoxin+4-aminopyrindine+barium chloride+glibenclamide+TEA) produced significant inhibition on the DG-induced response (P<0.01 for all); its maximum vasorelaxant effect (Imax) was reduced by 37, 24, and 30%, respectively. Preincubation of the artery rings with DG for 10 min produced concentration-dependent (1, 3 and 7 mg/ml) and total inhibition on the CaCl(2)-induced vasoconstriction.
  
  
  CONCLUSIONS
  These findings suggest the vasorelaxant effect of DG on rat basilar artery is independent of endothelium-derived mediators, whereas, inhibition of Ca(2+) influx in the vascular smooth muscle cells is important, and a minor component is mediated by the opening of K(ATP) channels. DG could be a useful cerebroprotective agent in some patients with occlusive cerebrovascular disease.
authors: School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong SAR, China. FrancisLam@cuhk.edu.hk
authors: F F Y
authors: FF
authors: Lam
authors: S Y
authors: SY
authors: Deng
authors: E S K
authors: ES
authors: Ng
authors: J H K
authors: JH
authors: Yeung
authors: Y W
authors: YW
authors: Kwan
authors: C B S
authors: CB
authors: Lau
authors: J C M
authors: JC
authors: Koon
authors: L
authors: L
authors: Zhou
authors: Z
authors: Z
authors: Zuo
authors: P C
authors: PC
authors: Leung
authors: K P
authors: KP
authors: Fung
mesh_terms: D000818:Animals; D001488:Basilar Artery / Q000187:drug effects*; D002851:Chromatography, High Pressure Liquid; D004305:Dose-Response Relationship, Drug; D004365:Drugs, Chinese Herbal / Q000302:isolation & purification / Q000494:pharmacology*; D066298:In Vitro Techniques; D008297:Male; D010618:Phenanthrolines / Q000302:isolation & purification / Q000494:pharmacology*; D018517:Plant Roots / Q000737:chemistry; D029908:Pueraria / Q000737:chemistry*; D051381:Rats; D017207:Rats, Sprague-Dawley; D027561:Salvia miltiorrhiza; D014664:Vasodilation / Q000187:drug effects*; D014665:Vasodilator Agents / Q000302:isolation & purification / Q000494:pharmacology*
chemical_list: D004365:Drugs, Chinese Herbal; D010618:Phenanthrolines; D014665:Vasodilator Agents; C028972:dan-shen root extract