Lithium block of outward current channels in Helix neurons

Outward currents were studied in isolated, perfused ganglion cells from Helix aspersa. Treatment with external solutions containing 40 mM LiCl slowed and reduced the delayed outward currents after about 15 min. The leak currents were reduced by external application of Li. Electrophoretic injection of LiCl increased the leak currents and reduced the net outward currents. From fits of a model with a rapid second-order current component and a slower first-order component, the effect of Li was to reduce the asymptotic current for the first component and double the activation time constant for the second component. This was equivalent to increasing the probability of entering the blocked state in a kinetic model of the K-channels. The slowness of the block suggested that Li might act through a chemical intermediate.