EFFECTS OF ALCOHOLS ON A-TYPE K+ CURRENTS IN LYMNAEA NEURONS

The effects of short-chain alcohols (methanol, ethanol and n-propanol) on the fast-inactivating, A-type, potassium current of Lymnaea neuron s were examined using macroscopic recording techniques. Alcohols produ ced a blockade of the current and modified its inactivation mechanism. The extracellular concentrations of methanol, ethanol and n-propanol causing 50% suppression of the current were 2970, 830 and 230 mM, resp ectively. The main effects of alcohols on inactivation were a decrease in the amplitude of the fast component and a simultaneous increase in the amplitude of the slow component of inactivation. In a model, the suppression of the fast component could be reproduced by an increase o f the backward rate constant related to the dissociation of the inacti vation particle from its binding site. The blockade and modification o f inactivation reveal similar dependences on ethanol concentration, in dicating that the same type of interaction of ethanol with the channel underlies both of these events. Ethanol was effective only in extrace llular applications. The data support an action of alcohols at a hydro phobic site near the extracellular portion of the channel.