1. ¹Department of Psychiatry, Bowles Center for Alcohol Studies, Curriculum in Neurobiology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
2. ²Department of Pharmacology, Bowles Center for Alcohol Studies, Curriculum in Neurobiology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA

Correspondence: Dr CW Hodge, Bowles Center for Alcohol Studies, Thurston-Bowles Building; CB No. 7178, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA. Tel: +1 919 843 4823; Fax: +1 919 966 5679; E-mail: chodge@med.unc.edu

³Present address: Department of Human Genetics, Emory University, Whitehead 301, 615 Michael Street, Atlanta, GA 30322, USA.

⁴Present address: Department of Pharmaceutical Sciences, University of Kentucky, 741 S Limestone, BBSRB B351, Lexington, KY 40536, USA.

Received 10 January 2008; Revised 15 May 2008; Accepted 16 May 2008; Published online 18 June 2008.

Abstract

Alcoholism and depression show high degrees of comorbidity. Clinical evidence also indicates that depression that emerges during abstinence from chronic alcohol use has a greater negative impact on relapse than pre-existing depression. Although no single neurobiological mechanism can account for the behavioral pathologies associated with these devastating disorders, converging evidence suggests that aspects of both alcoholism and depression are linked to reductions in hippocampal neurogenesis. Here, we report results from a novel preclinical behavioral model showing that abstinence from voluntary alcohol drinking leads to the emergence of depression-like behavior and reductions in neurogenesis. C57BL/6J mice were allowed to self-administer ethanol (10% v/v) vs H₂O in the home cage for 28 days. Alcohol was then removed for 1 or 14 days, and mice were tested in the forced swim test to measure depression-like behavior. After 14 days, but not 1 day of abstinence from alcohol drinking, mice showed a significant increase in depression-like behavior. The significant increase in depression-like behavior during abstinence was associated with a reduction in proliferating cell nuclear antigen (PCNA) and doublecortin (DCX) immunoreactivity in the dentate gyrus of the hippocampus indicating that both the number of proliferating neural progenitor cells (NPC) and immature neurons were reduced, respectively. The number of NPCs that were labeled with bromo-deoxyuridine (BrdU) at the beginning of alcohol exposure was not altered indicating that survival of NPCs is not linked to abstinence-induced depression. Chronic treatment (14 days) with the antidepressant desipramine during abstinence prevented both the emergence of depression-like behavior and the reduction in hippocampal neurogenesis indicating that abstinence-induced depression is associated with structural plasticity in the hippocampus. Overall, the results of this study support the conclusion that profound functional (ie behavioral) and structural changes occur during abstinence from alcohol use and suggest that antidepressant treatment may alleviate some of these pathological neurobehavioral adaptations.