ABSTRACT
Objective:To investigate the vasorelaxant effect of active fraction from compound Prunella vulgaris L. ( AFCP) on the i-solated thoracic aorta of rats and underlying mechanism. Methods:The study was performed with the tension experiment of the isolate rat thoracic aorta. The changes of vascular ring tension were measured by biological signal acquisition and analysis system, and the vasodila-tor effect of AFCP was observed. Results:AFCP(100-500μg·ml-1)could induce significant relaxation in aorta rings pre-contracted by phenylephrine (PE,1 μmol·L-1), and the relaxation effect was significant(75% ±8%) in endothelium-intact aortic and endothelium-denuded aortic. The vasodilatation effect of AFCP was not significantly affected by nitric oxide synthase ( NOS) inhibitor NG-nitro-L-argi-nine( L-NNA) , guanylate cyclase inhibitor MB,potassium channel blocker TEA and glibenclamide. In Ca2+-free bath solutions, AFCP (300 μg·ml-1 ) could shift downward dose-response curve of CaCl2 and significantly reduce the maximum contraction amplitude of PE. Conclusion:AFCP can relax rat aorta rings in a dose-dependent manner, which is endothelium-independent. The mechanism may be re-lated to the inhibition of intracellular calcium release and extracellular calcium flow, and has nothing to do with NO pathway, prostacyclin generation and calcium-activated potassium channels.