Cortical gamma-aminobutyric acid levels and the recovery from ethanol dependence: preliminary evidence of modification by cigarette smoking.

BACKGROUND

Gamma-aminobutyric acid (GABA)ergic adaptations contribute to the neurobiology of ethanol dependence and withdrawal. Clinical data suggest that tobacco smoking attenuates alcohol withdrawal symptoms. This study's objective was to measure time-dependent cortical GABA levels with sobriety in ethanol-dependent patients with mild to moderate withdrawal severity, controlling for alcoholism-related neurotoxicity and smoking.

METHODS

Proton magnetic resonance spectroscopy (MRS) was used to measure occipital cortical N-acetylaspartate (NAA), glutamate plus glutamine, and GABA in 12 ethanol-dependent men at approximately 1 week and 1 month of medication-free sobriety on an inpatient unit. Eight healthy men were studied once. The tissue composition of the MRS volume was determined.

RESULTS

Adjusting for less white matter in patients, GABA differed insignificantly between ethanol-dependent patients (smokers plus nonsmokers) and healthy subjects. In early sobriety, nonsmoking patients had more GABA than did smoking patients, but by 1 month, GABA decreased in nonsmokers without changing in smokers. Smoking was associated with increased glutamate plus glutamine in patients and healthy subjects, adjusting for NAA levels.

CONCLUSIONS

These data do not show that deficits in cortical GABA contribute directly to acute ethanol withdrawal. If smoking prevents withdrawal-related changes in cortical GABA systems, it may contribute to comorbidity of alcoholism and tobacco smoking.