GABAA receptor B subunit expression in the superior frontal cortex of human alcoholics

Full text: Changes in GABAA receptor pharmacology can be ascribed to alterations in expression of specific GABAA receptor subunits. Ethanol is known to be a potent agonist of the GABAA receptor. Chronic abuse of alcohol in humans results in damage of selective brain regions such as the superior frontal cortex (SFC), leading to neuronal cell loss. Studies in our laboratory 1 and elsewhere 2 have shown differences in expression of a number of GABAA receptor subunits in chronic human alcoholism. This suggests that alterations in GABAA receptor composition may be involved in the pathogenesis of alcoholic brain damage. We analysed the expression of the β1 ,β2 and β3 isoforms of the GABAA receptor by a competitive reverse transcription polymerase chain reaction (RT-PCR) technique, which utilised an internal standard (IS) for quantitation. 35 S-dATP was incorporated to enable visualisation of the PCR products. Human brain tissue was obtained at autopsy and stored in 0.32 M sucrose at -80 deg C. Total RNA was extracted from pathologically susceptible and spared regions, SFC and motor cortex respectively,of 22 control and 22 alcoholic patients. 1 μg of total RNA from each sample was co-amplified with 0.5 pg of IS and a ratio determined. A standard consisting of known amounts of β1 cRNA titrated against 0.5 pg of IS enabled a standard curve to be generated for quantitation of each unknown sample. The samples were subjected to polyacrylamide gel electrophoresis and the dried gel exposed to a phosphorimager screen. Data analysis was performed using the ImageQuant program. Initial results indicate that there is a reduction in expression of all the β transcripts in alcoholics when compared with controls, which supports the hypothesis that the GABAA receptor is altered by alcohol abuse. Supported by NHMRC. Copyright (2001) Australian Neuroscience Society