EFFECTS OF ETHANOL ON RECOMBINANT GABA CHANNELS

Project: Research project

Project Details

Description

Ethanol exerts its acute effects on the mammalian central nervous system
(CNS), at least in part, by altering the function of gamma-aminobutyric
acid GABA/a)-activated chloride channels (hence forward called GABA
channels). Molecular cloning studies have so far identified 12 distinct
GABA channel subunit isoforms and these isoforms are differentially
distributed in the CNS. This suggests different regions of the brain
assemble GABA channels from different combinations of subunits. Prior to
identification of the various isoforms, GABA channel heterogeneity was
suggested by the observation of functional subtypes (electrophysiology),
receptor subtypes (ligand binding), and apparent size subtypes
(electrophoresis). This raises the possibility that ethanol, by having
differential effects on the various GABA channels, might exert differential
effects on different brain regions. This project will combine molecular
biological and electrophysiological techniques and test this 'differential-
regulation' hypothesis by examining the actions of ethanol on GABA channels
of different subunit combinations. cDNAs encoding the GABA channel
subunits will be transcribed in-vitro and the cRNA will be injected, in
various combinations, into frog oocytes. Two-electrode voltage clamp
techniques will then be used to assess ethanol's modulation of currents
through the various GABA channels. Another fundamental question regarding the actions of ethanol on GABA
channels is the mechanism by which ethanol modulates GABA channels.
Ethanol could modulate either the ion-permeation properties or the opening
and closing kinetics (gating) of the GABA channel. Modulation of gating,
the more likely possibility, could result from a variety of mechanisms, one
example being a change in the stability of the open-pore conformation of
the channel. To test these and other putative modulatory mechanisms, the
patch-clamp technique will be used to record single GABA-activated ion
channels constructed from subunit combinations found to be ethanol
sensitive. A detailed analysis of single-channel data recorded in the
absence and presence of ethanol will suggest molecular mechanism(s) for
ethanol's modulation of GABA channels and will enable us to compare how
ethanol modulates GABA channels composed of different subunits. The long term objectives of this project are to determine the mechanisms by
which ethanol modulates GABA-activated ion channels in the CNS. This
information will increase our understanding of fundamental aspects of
ethanol's actions on synaptic inhibition in the CNS, and facilitate the
designing and testing of drugs to antagonize the intoxicating effects of
ethanol and treat various ethanol-related diseases, such as alcohol
withdrawal syndrome. Furthermore, comparison of the interactions of
ethanol with GABA channels of different subunit composition is a first step
towards identifying ethanol's specific sites of action on the GABA channel.
StatusFinished
Effective start/end date4/1/923/31/98

Funding

  • National Institutes of Health
  • National Institutes of Health
  • National Institutes of Health
  • National Institutes of Health: $84,685.00
  • National Institutes of Health
  • National Institutes of Health

ASJC

  • Medicine(all)

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