[Reversible elimination of K+ and Na+ currents at motor nerve terminals by SM486, a derivative of artemisinin].

Some derivatives of Artemisinin have been used as malariacides. Artemisinin derivative SM486 is water-soluble and has been shown also to have local anesthesia action. Here we report the effect of SM486 on Na+ and K+ channels at motor nerve terminals. Experiments were performed on mouse triangularis sterni nerve-muscle preparations. Presynaptic currents were picked up with a microelectrode inserted into the subendothelial space of the superficial nerve bundle under visual control using a x400 magnification water immersion objective. The results showed: (1) Both IK and INa were depressed in a dose-dependent manner, although the minimal effective concentration of SM486 for IK was lower than that for INa; (2) The depression was reversible as shown by the fact that the nearly completely blocked INa and IK currents could be restored to the control by simply washing away the perfusate SM486. (3) The decrease of IK was progressive, while the change of INa always began after IK proceeded to decrease rapidly. The effects of procaine on INa and IK are similar to SM486 but the effective concentration was higher.