| BACKGROUD: A marked reduction in systemic vascular resistance (SVR) and hypotension after intravenous bolus administration of remifentanil have been reported, which were not secondary to histamine release as in the case of morphine. These changes may not solely result from central nervous system inhibition or from centrally-mediated vagal stimulation. Otherwise, from a direct effect of relaxing the vascular smooth muscle, but the mechanisms are still unknown. The purpose of this study was to investigate the direct effect of remifentanil on the large-conductance cium-activated potassium currents (IBKCa) in human mesenteric arterial smooth muscle cells and understand partly the mechanisms by which remifentanil produces vasorelaxation. METHODS: Human mesenteric arterial smooth muscle cells were obtained freshly by the method of enzymolysis. Ca2+ -activated potassium currents (EBKCa) were separated with 5 mM 4-AP and were recorded by the whole-cell voltage-clamp technique. The effect of remifentanil on Ikca, at five different concentrations: 1.21 × 10-3μmol/L (C0.5) 4.84 × 10-3μmol/L (C2), 1.94 × 10-2 μmol/L(C8), 7.75×10-2μmol/L (C32), and 3.10×10-1μmol/L (C128), was observed and compared with the effect observed in the absence of remifentanil.
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