2160007

Benzodiazepine agonist and inverse agonist actions on GABAA receptor-operated chloride channels. I. Acute effects of ethanol.

Article date: 1990/5/1

PubMed ID: 2160007

Journal name: The Journal of pharmacology and experimental therapeutics (ISSN: 0022-3565)

ABSTRACT

Acute exposure to ethanol was found to enhance the ability of a benzodiazepine (BZ) inverse agonist, methyl-6,7-dimethoxy-4-ethyl-beta-carboline-3-carboxylate (DMCM), to reduce muscimol-activated 36Cl- uptake by membranes isolated from mouse cerebral cortex. Pretreatment in vivo with a hypnotic dose of ethanol (but not a subhypnotic dose), or exposure to a corresponding concentration in vitro, was effective. This increase in sensitivity of gamma-aminobutyric acid receptor-operated chloride channels to the actions of DMCM was due to an increase in both the potency and efficacy of DMCM. Sensitization to DMCM was reversible and was not observed 24 hr after a single injection of ethanol. Pretreatment with ethanol (10, 50 and 100 mM) in vitro produced sensitization to DMCM in a concentration-dependent manner, similar to that produced by in vivo exposure; this increase in sensitivity did not develop if the membranes were pretreated with ethanol at 0 degrees C. Similarly, in vitro exposure to pentobarbital (200 microM) or flunitrazepam (1 microM) enhanced the actions of the inverse agonist Ro15-4513 (ethyl-8-azido-5,6-dihydro-5-methyl-6-oxo-4H-imidazo[1,5a][1,4]BZ-3- carboxylate). Acute ethanol exposure did not alter low-affinity gamma-aminobutyric acidA receptor binding or muscimol action, or the ability of a BZ agonist, flunitrazepam, to augment muscimol-activated chloride flux. Ethanol exposure did not alter [3H]flumazenil (Ro15-1788) binding to central BZ receptors, its displacement by DMCM or allosteric modulation of DMCM binding by muscimol (muscimol-shift).(ABSTRACT TRUNCATED AT 250 WORDS)

This document is available from: http://directlinks.cc/files/muscimol/2160007.pdf

Author List: Buck K J, Harris R A

Publication Types: Journal Article; Research Support, U.S. Gov't, Non-P.H.S.; Research Support, U.S. Gov't, P.H.S.

Substances mentioned in the article: Carbolines; Chloride Channels; Chlorides; Convulsants; Membrane Proteins; Tritium; Benzodiazepines; methyl 6,7-dimethoxy-4-ethyl-beta-carboline-3-carboxylate; Ethanol; Flumazenil; Flunitrazepam;

Mesh terms: Animals; Benzodiazepines/antagonists & inhibitors; Brain/drug effects; Carbolines/pharmacology; Chloride Channels; Chlorides/metabolism; Convulsants/pharmacology; Ethanol/pharmacology; Flumazenil/metabolism; Flunitrazepam/pharmacology; Injections, Intraperitoneal; Male; Membrane Proteins/metabolism; Mice; Mice, Inbred ICR; Tritium;

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