Fig. 1.

Schematic of experimental design demonstrating the animal groups used and the time points for behavioral and histological analysis. Adult male Wistar rats were trained to self-administer ethanol (10 % v/v) for 2 weeks in a 30-min operant conditioning paradigm. The rats were then divided into two groups; one group was exposed to the chronic intermittent ethanol vapor (CIE) paradigm and are referred to as dependent rats (n = 15 rats). The second group was not exposed to CIE, and are termed nondependent rats (n = 18 rats). Both groups were maintained on ethanol self-administration sessions twice a week; this continued for 7 weeks. At the end of the 7th week, somatic withdrawal behaviors were scored. Three days after the cessation of CIE exposure, rats were injected with BrdU (150 mg/kg; i.p.) to label newly born cells. Two hours after BrdU injections, nine dependent and nine nondependent rats were euthanized, and their brains were processed for immunohistochemical analysis of BrdU cells. The remaining rats were maintained in their home cages for 4 weeks with no exposure to ethanol vapor or ethanol self-administration (abstinence). On days 28 and 29 during abstinence, these rats underwent 30-min ethanol self-administration session. Immediately after the last session, rats were euthanized and their brains were processed for BrdU immunohistochemistry