1. ¹Psychiatry and Behavioral Sciences, Stanford University School of Medicine, Stanford, CA, USA
2. ²Neuroscience Program, SRI International, Menlo Park, CA, USA
3. ³Radiology Department, Lucas MRS/I Center, Stanford University, Stanford, CA, USA
4. ⁴Department of Comparative Medicine, Stanford University School of Medicine, Stanford, CA, USA

Correspondence: Dr EV Sullivan, Psychiatry and Behavioral Sciences, Stanford University School of Medicine, 401 Quarry Road, Stanford, CA 94305-5723, USA. Tel: +1 650 859 2880; Fax: +1 650 859 2743; E-mail: edie@stanford.edu

Received 15 April 2008; Revised 8 July 2008; Accepted 13 July 2008; Published online 13 August 2008.

Abstract

Magnetic resonance spectroscopy (MRS) studies in human alcoholics report decreases in N-acetylaspartate (NAA) and choline-containing (Cho) compounds. Whether alterations in brain metabolite levels are attributable to alcohol per se or to physiological effects of protracted withdrawal or impaired nutritional or liver status remains unclear. Longitudinal effects of alcohol on brain metabolites measured in basal ganglia with single-voxel MRS were investigated in sibling pairs of wild-type Wistar rats, with one rat per pair exposed to escalating doses of vaporized alcohol, the other to vapor chamber air. MRS was conducted before alcohol exposure and twice during exposure. After 16 weeks of alcohol exposure, rats achieved average blood alcohol levels (BALs) of 293 mg per 100 ml and had higher Cho and a trend for higher glutamine+glutamate (Glx) than controls. After 24 weeks of alcohol exposure, BALs rose to 445 mg per 100 ml, and alcohol-exposed rats had higher Cho, Glx, and glutamate than controls. Thiamine and thiamine monophosphate levels were significantly lower in the alcohol than the control group but did not reach levels low enough to be considered clinically relevant. Histologically, livers of alcohol-exposed rats exhibited greater steatosis and lower glycogenosis than controls, but were not cirrhotic. This study demonstrates a specific pattern of neurobiochemical changes suggesting excessive membrane turnover or inflammation, indicated by high Cho, and alterations to glutamate homeostasis in the rat brain in response to extended vaporized alcohol exposure. Thus, we provide novel in vivo evidence for alcohol exposure as causing changes in brain chemistry in the absence of protracted withdrawal, pronounced thiamine deficiency, or severe liver damage.