ABSTRACT
Objective To evaluate the effects of different concentrations of dexmedetomidine on large-con-ductance Ca2+-activated K+ (BKca) channels in the rat mesenteric arterial smooth muscle (MASM) cells.Methods Sprague-Dawley rats of both sexes,weighing 180-220 g,were used in this study.Single MASM cell was freshly isolated from mesenteric arteries in two steps.Ten cells were chosen and studied.When holding potential was 40 mV and the concentration of free calcium ions was 10-7 mol/L,inside-out patch-clamp technique was used to record the single BKCa channel current before and after application of different concentrations of dexmedetomidine (0,10-9,10-8,10-7,10-6,10-5 mol/L).Total open probability (NPo),amplitude (Am),mean open time (To) and mean close time (To) of single BKca channel were observed and recorded.Results Compared with the baseline value,dexmedetomidine 10-7,10-6 and 10-5 mol/L increased NPo in a concentration-dependent man-ner,and dexmedetomidine 10-9,10-8,10-7,10-6,10-5mol/L shortened Tc (P ＜0.05 or 0.01).Compared with the value obtained when the concentration of dexmedetomidine was 10-9 mol/L,Tc was significantly shortened when the concentration of dexmedetomidine was 10-8 mol/L (P ＜ 0.05),and no significant change was found in Am and To obtained when different concentrations of dexmedetomidine were applied (P ＞ 0.05).Conclusion Dexmedetomidine 10-7,10-6 and 10-5 mol/L activate BKca channels in rat MASM cells in a concentration-depen-dent manner,which is one of the mechanisms of decrease in blood pressure by dexmedetomidine.