Altered GABA_A Receptor Subunit and Splice Variant Expression in Rats Treated With Chronic Intermittent Ethanol

Abstract

Changes in GABAA receptors were found in rats given CIE. Increased alpha6 subunit in the cerebellum was demonstrated by using both the binding to diazepam-insensitive sites for [3H]Ro15-4513 and increased levels of the 57-kDa alpha6 polypeptide after photoaffinity labeling with this ligand. This increase appeared after 30 doses of ethanol and decayed to normal 1 week after ethanol was discontinued. The transient change in cerebellar alpha6 subunit-containing receptors, also reportedly seen after chronic continuous ethanol, is thus unlikely to account for the persistently hyperexcitable, kindled, seizure-susceptible state seen in CIE. However, the significant decrease in gamma2 subunit L/S splice variant ratio in the hippocampus implies changes in GABAA receptor function, possibly involving protein phosphorylation by protein kinase C. Altered receptor trafficking and turnover associated with synaptic plasticity may contribute to the observed reduced inhibition in the hippocampus and other signs of alcohol dependence produced by CIE.

Therapeutic potential of antisense oligonucleotides as modulators of alternative splicing

“…The GABA A γ2 gene is alternatively spliced to generate a short (γ2S) and a long (γ2L) form. It was recently shown that the ratio of γ2S to γ2L is severely reduced in the prefrontal cortex of schizophrenia patients (24) and in animal models of alcoholism (25). This suggests that reduction of the levels of the long form, in addition to increases in the levels of the short form, could be of clinical benefit (Figure 1b).…”

SB242084, flumazenil, and CRA1000 block ethanol withdrawal–induced anxiety in rats

“…The inactivity of zolpidem in the current experiments also supports the suggestion of involvement of non-type 1 benzodiazepine receptors in this flumazenil effect, which was most marked at higher doses. It is known that various binding sites have differential affinities for and responses to flumazenil (Barnard et al, 1998), and potential structural adaptations of GABA receptors in select cells or brain regions after chronic ethanol treatment [see, for example, Grobin et al (2000), Papadeas et al (2001), and Petrie et al (2001)] may mediate these differences. Furthermore, results of the dose-ranging and drug-treated control experiments demonstrate that the antianxiety actions during withdrawal can occur without correcting locomotor deficits in the plus-maze or social interaction test or without having actions on anxiety in control animals.…”

The role of GABAA receptors in the development of alcoholism

“…CIE rats show GABA A receptor changes specifically in the hippocampus, including decreased α 1 and δ subunit peptide expression (Cagetti et al, 2003) and elevated mRNA levels of α 4 , γ 1 and the short splice variant (γ 2S ) of γ 2 (Cagetti et al, 2003;Mahmoudi et al, 1997;Petrie et al, 2001). A model of chronic ethanol consumption (40 days) has also been shown to increase α 4 subunit (but no other subunit) peptide expression in the hippocampus .…”