The Effects Of The Volatile Oil Of Nardostachys Chinensis Batal On L-type Ca²⁺ Channel Of Isolated Ventricular Myocytes In Rats

Objective:To study the effects of the Volatile Oil of Nardostachys Chinensis Batal (VONCB) on L-type Ca²⁺ channel of isolated ventricular myocytes in the rats.To explore the anti-arrhythmic mechanisms of VONCB.Methods:Ventricular myocytes were obtained enzymatically from SD(Sprague Dawley) rats. In brief, a rat (weight 200-300 g) was anesthetized with chloral hydrate (300mg/kg i.p). The dissected heart was mounted on a Langendorff apparatus and perfused first with nominally Ca²⁺free Tyrode solution for 5 min, and then with Ca²⁺free Tyrode solution containing collagenaseâ… and pronase E(50μmol/L ) for 25–35 min. The enzyme solution was then washed out with low Ca²⁺ solution(200μmol/L)and the ventricular myocytes were dispersed and filtered through a nylon mesh, finally stored in KB solution. L-Type Ca²⁺ channels were recorded using the whole-cell configuration of the patch-clamp technique.Results:1. The VONCB reduced the current of I_Ca-L with dose-dependent block relationship. At concentrations of 3, 5, 10, 20 and 50μg/g, the peak current of I_Ca-L was, respectively, reduced by (11.18±1.48)% ,(n=5, P<0.05), (24.83±4.82)%,(n=5, P<0.05), (45.72±3.54%) (n=5,P<0.05) ,(76.87±7.03)%, (n=5, P<0.05) and (100±0)%,(n=5,P<0.05)at membrane potential of +10 mV.2. The current density of I_Ca-L was impacted with 10μg/g of the VONCB. The peak current density of I_Ca-L was reduced to (5.67±0.78)pA/pF from (10.17±1.49)pA/pF The I-V curve was shifted upward, but the active potential, peak potential and reverse potential were not changed.3. The activation curve of I_Ca-L has significant change at 10μg/g of the VONCB. The activation curve was moved to more positive potential. V_1/2 of I_Ca-Lwas to -2.77±049 mV from -5.47±0.50 mV (n=5,P<0.05),and the slope was to 4.50±0.40 from 4.68±0.39(n=5,P>0.05). 4. The inactivation curve of I_Ca-L has significant change at 10μg/g of the VONCB. The inactivation curve moved to more negative potential. V_1/2 of I_Ca-L was to -29.44±1.03mv from -20.82±0.48mv(n=5 P<0.05),and the slope was to 11.05±0.86 from 6.16±0.43 (n=5,P<0.05).Conclusion:1.The VONCB decreases the L-Type Ca²⁺ channel current in a dose-dependent manner.2.The current-voltage curve was shifted upward,but the shape of the curve and active potential peak potential and reverse potential were not changed.3.The activation curve was shifted towards the depolarizing direction.4.The inactivation curve was shifted towards the hyperpolarizing direction.