ETHANOL DECREASES THE TETRAETHYLAMMONIUM- INDUCED BLOCKADE OF POTASSIUM CHANNELS IN MOLLUSCAN NEURONS

A high threshold K+ current was recorded in isolated neurons of land s nail using the two microelectrode voltage clamp method. KC current con sisted mainly of two components, slow Ca2+- dependent K+-current (I-K( Ca)) and more fast Ca2+-independent K+-current (I-K(V)), the ratio of which varied from cell to cell, The influence of acute ethanol exposur e on the blocking effects of K+ antagonists was studied. The following K+ antagonists were used: tetraethylammonium (TEA), 4-aminopyridine ( 4-AP) and quinine. Ethanol (2-200 mM) either produced no effect on the total K+ current or inhibited it by 6-20%, When applied in the presen ce of 4-AP or quinine, ethanol did not affect the blocking effect of t hese antagonists on K+ current, while the blocking effect of 0.1-5 mM TEA on both I-K(Ca) and I-K(V) rapidly (1-2 min) decreased after 2-200 mM ethanol application (n = 10/14). The deblocking effect of ethanol was tonic in one group of the cells and transient one in another group of the cells. The effect persisted when TEA concentration increased, This suggests a noncompetitive character of interaction between TEA an d ethanol.