Persistent high alcohol consumption in alcohol-preferring (P) rats results from a lack of normal aversion to alcohol

Abstract

Aims: In this study, we tested the impact of pretreatment with alcohol on subsequent alcohol drinking in outbred Sprague-Dawley and selectively bred alcohol-preferring (P) rats.

Methods: As a pretreatment, male Sprague-Dawley and P rats were given a passive oral administration of either alcohol (1.0 g/kg) or tap water. Then, they were given free choice of drinking alcohol (5% v/v) or water in their home cages, which was measured over 4 weeks.

Results: Without alcohol pretreatment, there was no significant strain difference in alcohol preference; both strains preferred 5% (v/v) alcohol solution. The strain difference was only apparent in the groups given alcohol pretreatment. This arose from the fact that alcohol pretreatment significantly reduced alcohol preference in the Sprague-Dawley rats to a level well below 50%, while it did not alter drinking behavior in P rats. The same effects were seen with total alcohol consumption (g/kg/day). These effects persisted throughout the 4 weeks of the study.

Conclusions: The principal difference between the Sprague-Dawley and P rats was that the P rats did not show the normal aversion to alcohol after forced exposure to alcohol that the Sprague-Dawley rats showed. One of the potential contributors to high alcohol intake and preference in P rats may be lack of sensitivity to aversive effects of alcohol.

Fig. 1

(A) Effects of an oral dose (1 g/kg) of alcohol administration on subsequent alcohol intake (g/kg/day) in alcohol-preferring P and Sprague–Dawley rats. Data represent the means ± SEM of 4 weeks. N = 8 for each group of Sprague–Dawley rats, 9 for vehicle-treated P rats and 6 for alcohol-treated P rats. (B) Effects of an oral dose (1 g/kg) of alcohol administration on subsequent alcohol preference in alcohol-preferring P and Sprague–Dawley rats. Data represent the means ± SEM of 4 weeks. N = 8 for each group of Sprague–Dawley rats, 9 for vehicle-treated P rats and 6 for alcohol-treated P rats.

Fig. 2

(A) Effects of one single oral dose (1 g/kg) of alcohol administration on subsequent alcohol intake (g/kg/day) in alcohol-preferring P and Sprague–Dawley rats. Data represent the means ± SEM of weekly intake for 4 weeks. N = 8 for each group of Sprague–Dawley rats, 9 for vehicle-treated P rats and 6 for alcohol-treated P rats. (B) Effects of one single oral dose (1 g/kg) of alcohol administration on subsequent preference for alcohol in alcohol-preferring P and Sprague–Dawley rats. Data represent the means ± SEM of weekly intake for 4 weeks. N = 8 for each group of Sprague–Dawley rats, 9 for vehicle-treated P rats and 6 for alcohol-treated P rats.