[Mechanisms of prolonged action potential generation in barium solutions]

The membrane currents were recorded under voltage clamp from identified nerve cells of the Helix pomatia. The replacement of the external Ca ions in normal solution by Ba ions produced a shift in the potassium conduction-voltage curve along the voltage axis in the positive direction. The decrease in the limiting value of the potassium conduction was also observed. In Na-Ca-free solutions containing Na ions but no other divalent cations the inward membrane current was recorded. This current was separated into two components: an early fast inactivating (I) and a smaller long lasting component (II). It seems that the prolongation of the action potential in barium solution is due to the suppression of K conduction by Ba ions and to the existence of the long-lasting inward current.