Ž.
Brain Research 751 1997 102–112
Research report
Expression of the
a
,
a
and
a
isoforms of the GABA receptor in human
12 3 A
alcoholic brain
Joanne M. Lewohl
a,b
, Denis I. Crane
b
, Peter R. Dodd
a, )
a
Clinical Research Laboratory, Royal Brisbane Hospital Research Foundation, Griffith UniÕersity, Brisbane, Australia
b
School of Biomolecular and Biomedical Science, Griffith UniÕersity, Brisbane, Australia
Accepted 12 November 1996
Abstract
The expression of the
a
,
a
and
a
isoforms of the GABA receptor was studied in the superior frontal and motor cortices of 10
12 3 A
control, 10 uncomplicated alcoholic and 7 cirrhotic alcoholic cases matched for age and post-mortem delay. The assay was based on
competitive RTrPCR using a single set of primers specific to the
a
class of isoform mRNA species, and was normalized against a
synthetic cRNA internal standard. The assay was shown to be quantitative for all three isoform mRNA species. Neither the patient’s age
nor the post-mortem interval significantly affected the expression of any isoform in either cortical area. The profile of expression was
shown to be significantly different between the case groups, particularly because
a
expression was raised in both groups of alcoholics cf
1
controls. The two groups of alcoholics could be differentiated on the basis of regional variations in
a
expression. In frontal cortex,
a
11
mRNA expression was significantly increased when uncomplicated alcoholics were compared with control cases whereas alcoholic-cirr-
hotic cases were not significantly different from either controls or uncomplicated alcoholic cases. In the motor cortex,
a
expression was
1
elevated only when alcoholic-cirrhotic cases were compared with control cases. There was no significant difference between case groups
or areas for any other isoform. q 1997 Elsevier Science B.V. All rights reserved.
Keywords: Brain damage; Pathogenesis; Cerebral cortex; Cirrhosis of the liver; Human; mRNA; Quantitative RTrPCR
1. Introduction
In human subjects, chronic, long-term, excessive inges-
tion of alcohol is associated with selective neuronal losses
and changes in neurotransmitter systems. Morphometric
analysis at post-mortem revealed a 22% decrease in the
number of neurones in the superior frontal cortex of
chronic alcoholic cases, as compared with an unaffected
area, such as the primary motor cortex, in the same cases
or with the homotropic area in non-alcoholic control cases
wx
16 . In addition, there was a reduction in the mean
neuronal surface area in both cortical areas, indicating that
Abbreviations: RTrPCR, reverse-transcriptase polymerase chain reac-
tion; DEPC, diethyl pyrocarbonate; dH O, autoclaved pure water; TBE,
2
Tris-borate-EDTA; DTT, dithiothreitol; SSC, standard saline citrate; SDS,
sodium dodecylsulfate; PMD, post-mortem delay; M, male; F, female;
OD, drug overdose
)
Corresponding author. Clinical Research Laboratory, Royal Brisbane
Hospital Research Foundation, Bancroft Centre, Brisbane Q4029, Aus-
Ž.
tralia. Fax: q61 7 362 0108; E-email: peterd@qimr.edu.au
wx
shrinkage of these cells had occurred 16 . These findings
suggest that specific neuronal populations may be suscepti-
ble to damage in chronic alcoholism.
Alcohol is rapidly incorporated into biological mem-
branes and can cause changes in ion channel, receptor and
neurotransmitter functions in in vitro experiments. Ligand
binding studies using human autopsy tissue have shown
that binding to the GABA site is significantly greater in
A
the superior frontal cortex of non-cirrhotic alcoholic cases,
as compared with either the same region in control cases
or with the motor cortex of the same case. This increase in
binding appears to reflect an increase in the density of both
Ž.
agonist high-affinity GABA and benzodiazepine
Ž.wx
‘central-type’ sites 10 although there were discrepancies
between the results obtained with different ligands, and
when case groups with different diseases commonly asso-
wx
ciated with alcohol abuse were included 8,10 . GABA
enhancement of benzodiazepine binding was also altered
wx
in the superior frontal cortex of alcoholics 8 . Thus, there
may be a functional uncoupling of the GABA rbenzodi-
A
azepine receptor complex.
0006-8993r97r$17.00 Copyright q 1997 Elsevier Science B.V. All rights reserved.
Ž.
PII S0006-8993 96 01396-0