Abstract
The effects of short-chain alcohols (methanol, ethanol andn-propanol) on the fast-inactivating, A-type, potassium current of Lymnaea neurons were examined using macroscopic recording techniques. Alcohols produced 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, respectively. 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 of the backward rate constant related to the dissociation of the inactivation particle from its binding site. The blockade and modification of inactivation reveal similar dependences on ethanol concentration, indicating that the same type of interaction of ethanol with the channel underlies both of these events. Ethanol was effective only in extracellular applications. The data support an action of alcohols at a hydrophobic site near the extracellular portion of the channel.
Footnotes
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Send reprint requests to: Marvin C. Ziskin, Center for Biomedical Physics, Temple University Medical School, 3400 North Broad Street, Philadelphia, PA 19140.
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↵1 This work was supported by a grant from the Richard J. Fox Foundation.
- Abbreviations:
- Iaf
- fast-inactivating potassium A-current
- TEA
- tetraethylammonium ion
- Received August 5, 1996.
- Accepted December 16, 1996.
- The American Society for Pharmacology and Experimental Therapeutics
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