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 a subunit genes of the GABAA receptor in the SFC of human alcoholic brain, suggesting that differences in GABAA receptor subunit expression could give rise to the locally altered GABAA pharmacology which is associated with alcohol abuse. A competitive RT-PCR assay has been developed to study the expression of the GABAA receptor beta-subunit genes beta1, beta2, and beta3. 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 GABAA 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.

Concentrations of transferrin and carbohydrate-deficient transferrin in postmortem human brain from alcoholics.

Transferrin (T f) and its carbohydrate-deficient isoform (CDT) were measured by radioimmunoassay in phosphate-buffered saline extracts of two informative areas of cerebral cortex tissue obtained at autopsy from alcoholics without other associated disease (n = 4); alcoholics with cirrhosis of the liver (n = 4) and agematched controls (n = 4). Total T f was also measured in two informative cortical areas from five dementia cases. All cases were male. Total immunoreactive T f was assayed directly in the extract, CDT immunoreactivity in the concentrated eluate after the sialylated form was removed by passing through DEAE-Sephacel at pH 5.65. Brain CDT averaged 10% of total T f overall. Although replicate extractions of individual samples gave consistent assays for both substances, there was wide variation both between different cortical areas from a given case and between cases within groups. There were no significant differences between total T f levels in uncomplicated alcoholics, dementia cases and controls, but cirrhotic alcoholics gave significantly higher values. The CDT: T f ratio was not increased in the brains of either group of alcoholics compared to controls. Whereas the serum CDT: T f ratio is an excellent marker of recent alcohol consumption, brain T f and CDT concentrations do not mark alcoholism nor dementia, and their biological variability diminishes their usefulness as disease indices. However, brain T f may be a marker of cirrhosis-induced changes.