Abstract: Objective: To observe the effect of extracellular Ba²⁺ on the recording L-type calcium channel of rat ventricular cardiocytes.Methods: Whole-cell patch clamp technique was used to record the currents of L-type calcium channels (I_Ca,L) in a single ventricular cardiocyte isolated from a rat heart by acute enzymatic digestion combined with mechanical method. Ba²⁺ was used to replace Ca²⁺ in Tyrode's solution, and Ba²⁺ (0~0.8 mmol/L) was directly added to Tyrode's solution to observe the change of the peak current within 15 minutes. The data were repeated with 5 cells or more.Results: ①The inactivation rate of I_Ca,L was slowed down significantly (P<0.01) with Ba²⁺ instead of Ca²⁺ gradually in Tyrode's solution. There was no change in the inactivation rate of I_Ca,L when the Ba²⁺ (0.2, 0.4 mmol/L) was added in the extracellular solution, but when 0.8 mmol/L Ba²⁺ was added, the inactivation rate would slow down significantly (P<0.01). ②Ba²⁺(0.2, 0.4 mmol/L) added in the extracellular solution could decrease the peak current attenuation. Compared with the group in Tyrode's solution, the peak current attenuation rate of the group in Ba²⁺ (0.2, 0.4 mmol/L) added in the extracellular solution was decreased significantly at the two time points (10 min, 15 min, P<0.01). ③The extracellular Ba²⁺ (0.4 mmol/L) could move the current-voltage curve down, change the reversal potential, weaken I_Ca,L inhibition induced by salvianolic acid A and right-shift concentration-response curve.Conclusion: The addition of Ba²⁺ to extracellular solution can attenuate the peak current decay, change the voltage-dependent characteristics of calcium channels and influence drug dose-effect relationship when whole-cell patch clamp technique is used to record L-type calcium channel of rat ventricular cardiocytes.

Key words: rat, ventricular myocytes, Ba²⁺, L-type calcium current, whole-cell patch clamp