Effect of methamphetamine on potassium and L-type calcium currents in rat ventricular myocytes

The mechanisms of cardiac toxicity caused by methamphetamine (MA) are poorly understood at present. This study was designed to investigate the effects of MA on ionic currents in myocardial cells. The effects of MA on transient outward potassium current (I-to), inward rectifying potassium current (I-K1), and L-type calcium current (ICa-L) in isolated rat ventricular myocytes were studied using the whole-cell patch clamp technique. It was demonstrated that MA inhibited the I-to, I-K1, and ICa-L in the rat ventricular myocytes concentration-dependently. MA shifted left the I-to steady-state inactivation curve and shifted down the recovery curve, but had no influence on the steady-state activation curve. MA did not affect the ICa-L steady-state activation curve or steady-state inactivation curve, but shifted down the recovery curve. We concluded that MA had inhibitory effects on the I-to, I-K1, and ICa-L in ventricular myocytes, which might be one of the possible electrophysiological mechanisms of cardiac damage caused by MA.