Multiple Factors Affecting Volitional Consumption of Alcohol in the Abrams Wistar Rat

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Abstract
Alcohol preference of rats was studied using a multiple-factor design. Fifty-six male and female Wistar albino rats, divided into experimental and control groups, were used. The ratio of the intake of a 10% solution of ethanol to total fluid was measured in the 2 groups under 5 experimental conditions: initial preference (a 14-day free-choice situation), stress (an 8-day free-choice situation during which the experimental rats were removed from their home cages and shocked 5 times daily), forced intake (an 8-day period during which water and alcohol were available to all rats on alternate days and experimental rats were shocked as previously), stress, identical to the 1st stress conditions, and a final 14 days of free-choice consumption. All rats were fed ad libitum a diet of Purina Chow and were caged individually. The positions of the fluid tubes were alternated daily. Neither sex nor group differences in absolute consumption of alcohol were found during the initial choice period. While there were no sex differences in water consumption, males tended to consume greater amounts of alcohol than females. Average water intake by males during the free-choice experimental periods ranged from 20. 81 to 25. 59 ml, and from 21. 75 to 27.21 by females. Average alcohol intake ranged from 1.55 to 10.27 ml by males and from 1. 75 to 6. 45 ml by females. An analysis of variance for sex, treatment groups, and experimental conditions yielded significant differences with regard to consumption under the different conditions and by sex, with males showing the highest ratio of alcohol consumption. An increased ratio of alcohol consumption by females as a function of stress and a decreased consumption by males were also demonstrated. When the rats from both groups were divided into low and high consumers on the basis of group median intake of alcohol during the base-line period, it was found that initially high consumers took increasing amounts of alcohol regardless of experimental conditions while initially low consumers increased their consumption only after a period involving forced intake. The latter increase in consumption was discussed in terms of "experience" with alcohol afforded by the forced-intake period. The results indicate that several factors may be operating simultaneously to affect free-choice alcohol consumption in the rat, but that the most significant factor appears to be initial preference or aversion. The results suggest also that a free-choice consumption could be profitably investigated using sex differences in response to stress as an additional variable.