Alcohol consumption in free-feeding rats: procedural, genetic and pharmacokinetic factors

Voluntary consumption of alcohol by rats (i.e. in the absence of food or water deprivation, sweetening of the alcohol solution, etc.) that results in the attainment of behaviorally significant or pharmacologically detectable blood alcohol levels (BALs) has been difficult to demonstrate. In this study, we showed that free-feeding Wistar rats given access to increasingly concentrated solutions of alcohol in separate "drinking" cages on a 1-h per day basis drank on average close to 1 g/kg, resulting in average BALs close to 50 mg%. This drinking was comparable to that obtained by rats trained according to a procedure used widely by others in which animals are maintained at reduced body weights. Weight restriction alone, however, did not enhance amount of alcohol consumption over that of free-feeding animals in the 1-h session. There was also a strain difference in that Wistar rats drank significantly more than did Sprague-Dawley rats. Post hoc absorption curves showed that the initial absorption of alcohol from both the stomach and the peritoneum was slower in Wistar than in Sprague-Dawley rats, suggesting rate of absorption may be inversely related to amount of alcohol consumed; metabolic rates and volumes of distribution appeared unrelated to consumption. This periodic availability paradigm might be useful to investigate the effect of biological variables on individual bouts of alcohol consumption.