Effects Of The Volatile Oil Of Nardostachys Chinensis On Transient Outward Potassium Membrane Current In Isolated Ventricular Myocytes Of Rat

Objective:To study the effects of the volatile oil of Nardostachys chinensis(VONC) on transient outward potassium current (Ito) in isolated ventricular myocytes of rat. Including: dose-response curves, I-V curves, acivation curves and inactivation curves.Methods:Rat was sacrificed after anesthesia with pentobarbital first.The heart was quickly removed and hung on a Langendorff apparatus, and perfused initially with Ca2+ free Tyrode's solution, then perfused with enzymatic solution. As soon as the heart became softened, the ventricle most of rat was cut into nubs and blown with sucker in KB solution to obtain ventricular myocytes of rat. The whole-cell patch clamp was used to record the change of currents of Ito comparing effects with different dose of the volatile oil of Nardostachys chinensis.Results:1. The volatile oil of Nardostachys chinensis reduced the current of Ito with dose-dependent block relationship. At concentrations of 3, 6, 10 and 20μg/g, the peak current of Ito was, respectively, reduced (27.01±6.93%, n=5, P<0.05), (51.13±9.82%, n=5, P<0.05), (80.86±4.63%, n=5, P<0.05) and (94.81±4.30%, n=5, P<0.05) at menbrane potential of +70mV.2. The current density of Ito was impacted by the concentration at 6μg/g of the volatile oil of Nardostachys chinensis. The peak current density of Ito was reduced to 11.23±1.47pA/pF from 23.08±0.74pA/pF (n=5, p<0.05) at menbrane potential of +70mV in 6μg/g of the volatile oil of Nardostachys chinensis. It was reduced about 50%.3. The activation curve of Ito has no significant change in 6μg/g of the volatile oil of Nardostachys chinensis. The 50% of activation voltage of Ito was to 32.23±4.41 mV from 36.17±3.36 mV (n=5,P> 0.05) and slope was to 28.75±4.50 from 24.00±2.79 (n=5,P> 0.05).4. The inactivation curve of Ito has significant change in 6μg/g of the volatile oil of Nardostachys chinensis. The 50% of inactivation voltage of Ito was to -40.54±0.70 mV from -33.74±0.48 mV (n=5, P<0.01) and slope was to 8.42±0.62 from 5.00±0.40 (n=5, P<0.01).Conclusions:1. The inhibition of the Ito current in isolated ventricular myocytes of rat after using the volatile oil of Nardostachys chinensis is dose-dependent block relationship;2. The I-V curve of Ito has been move down after using the volatile oil of Nardostachys chinensis;3. There is no significant change in the activation of Ito after using the volatile oil of Nardostachys chinensis;4. The inactivation curve of Ito shift to the negative direction after using the volatile oil of Nardostachys chinensis. The volatile oil of Nardostachys chinensis blocks the current of Ito, which may change the effective refractory period of ventricular myocytes of rat, and it may be contribute to some antiarrhythmic effects.