Mechanisms of the relaxant effect of a Danshen and Gegen formulation on rat isolated cerebral basilar artery

Aim of the studyDanshen (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.Materials and methodsRat 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 Ca2+ channels were investigated in artery rings incubated with Ca2+-free buffer and primed with 100 nM U46619 for 5 min prior to adding CaCl2 to elicit contraction.ResultsDG produced concentration-dependent relaxation of the artery rings with an IC50 of 895 ± 121 μg/ml. Mechanical removal of the endothelium or pretreatment with the BKCa channel inhibitor iberiotoxin (100 nM), the KV channel inhibitor 4-aminopyridine (1 mM), or the KIR channel inhibitor barium chloride (100 μM), all had no effect on the DG-induced response (P > 0.05 for all). However, pretreatment with the KATP 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 CaCl2-induced vasoconstriction.ConclusionsThese findings suggest the vasorelaxant effect of DG on rat basilar artery is independent of endothelium-derived mediators, whereas, inhibition of Ca2+ influx in the vascular smooth muscle cells is important, and a minor component is mediated by the opening of KATP channels. DG could be a useful cerebroprotective agent in some patients with occlusive cerebrovascular disease.

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