Expression of GABA A receptor isoform genes in the cerebral cortex of cirrhotic and alcoholic cases assessed by S 1 nuclease protection assays

Abstract

Pathogenic processes underlying the localized reduction in neuronal number in cerebral cortex in human alcoholics have been reported to be associated with selective variations in the parameters of GABA A receptor site binding. Since the properties of the receptor complex depend on its isoform composition, we studied how the expression of GABA A receptor subunit isoform genes varied with alcoholism. Cerebral cortex tissue was obtained at autopsy from chronic human alcoholics (average ethanol intake > 80 g/day for most of their adult lives; n = 17) and matched controls (< 20 g/day ethanol; n = 15). Eight of the alcoholics and five of the controls had pathologically confirmed cirrhosis of the liver. Expression of α 1, α 2, α 3, α 5, β 1, β 3, and γ 2 GABA A mRNA was assessed by S 1 nuclease protection assays. After phosphorimager quantitation and normalization to GAPDH mRNA and 18S rRNA, none of the mRNA species showed significantly different expression in uncomplicated alcoholics. Analysis of differences in the patterns of expression of the various subunits showed the α 1 signal was strongest in combined cirrhotic motor cortex while the α 3 and β 3 values were greatest in combined cirrhotic frontal cortex. It appears that only major differences in mRNA expression may be detected by this technique in human brain.