Expression and distribution of GABAA receptor subtypes in human alcoholic cerebral cortex

Long-term alcohol abuse is known to target specific areas of the brain such as the superior frontal cortex (SFC), resulting in neuronal cell loss. Abnormal transmission of the inhibitory neurotransmitter GABA may contribute to this damage. Previous work in our laboratory has found differential expression and distribution of certain alpha subunit genes of the GABA(A) receptor in the SFC of human alcoholic brain, suggesting that differences in GABA(A) receptor subunit expression could give rise to the locally altered GABA(A) pharmacology which is associated with alcohol abuse. A competitive RT-PCR assay has been developed to study the expression of the GABA(A) receptor beta -subunit genes beta (1), beta (2), and beta (3). A single set of primers homologous to all three beta isoform sequences has been shown to amplify each of the beta isoforms from mRNA isolated from human brain tissue obtained at autopsy. An internal standard has been designed which is identical to the target except for a 61-bp deletion and a unique restriction enzyme (RE) site. This is co-amplified with the target sequences to allow amplification efficiency to be assessed and thus enable the quantitation of gene expression. A range of GABA(A) receptor ligands were used to look at differential distribution of receptor subtypes in the cortical laminae by autoradiography. Differences in distribution of the ligands were demonstrated, consistent with a hypothesis of alcohol-induced variations in the expression of receptor subunits.