Effect of single ethanol administration on the behavior, consumption, and preference of ethanol in tame and aggressive rats

According to the stress relief hypothesis, a high level of anxiety or stress may cause greater alcohol consumption and alcohol addiction. However, the data obtained with experimental animals do not always confirm this statement. Strains of Norway rats selected for tame and aggressive attitude to humans can serve as a model for investigating relationships between anxiety, the function of the hypothalamic–pituitary–adrenal (HPA) system, and predisposition to alcohol addiction. Former studies of tame rats, based on the blood levels of the corticosterone and adrenocorticotropic hormone (ACTH) at rest and under stress, revealed a decrease in the manifestation of anxiety-like behavior and in the HPA function compared to aggressive and unselected rats. This work assesses the preferred consumption of ethanol at various concentrations with free access to ethanol and water (two-bottle choice test) and the effect of acute ethanol administration on the behavior of aggressive and tame male rats in an elevated plus maze (EPM). After intraperitoneal alcohol administration, tame and aggressive males show a reduced number of rearings in the center of the EPM, but the reduction is statistically significant only in the former. It points not only to the absence of the anxiolytic action of 12% ethanol but also to an enhancement of anxiety-like behavior in tame rats. After the withdrawal of alcohol for seven days, tame rats show signs of deprivation, because the alcohol consumption becomes greater than before the withdrawal. Thus, the difference between tame and aggressive rats during alcohol consumption varies with the alcohol concentration. Aggressive males drink more alcohol than water only at the 2% concentration. Hence, the hypothesis of stress relief is confirmed only for this concentration