Conditions Affecting Voluntary Alcohol Consumption in Rats

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Abstract
Ninety-five male and female laboratory rats, the offspring of parents match-bred for tendencies toward flexibility or rigidity on a behavioral test, were raised from 19 to 60 days of age in environments varying in degree of social isolation, restriction of motor activity, and intensity of incoming sensory stimulation. One-half of the prematurely weaned animals had access to a weak alcohol-in-milk solution (increasing from 2 to 5%) during this period. The balance of the animals had a milk solution available without the alcohol. From 60 days through 180 days of age all animals were individually caged with both water and alsohol-in-water (increasing gradually in concentration from 5 to 15%) freely available. Daily reading of quantities of each beverage consumed by each animal were recorded throughout this period. From 60 days of age through 150 days, several rats from each of the former groups were subjected to intensive training and testing with Hebb-Williams maze problems and problems using the Lashley jumping stand, then to insoluble jump stand problems to provide them with stressful experiences. The balance of the animals were given no special handling. Individual ratios of alcohol: water ranged from almost total abstinence (.09) to a 3:1 preference for alcohol (3.29), 1/3 of the animals consistently preferring alcohol to water. Males drank significantly more alcohol than females, animals from parents match-bred for flexibility drank more than those from rigid matchbred parents, and stressed rats had higher alcohol: water ratios than nonstressed rats (p''s all < .02). Early exposure to alcohol increased alcohol consumption only with nonstressed males from the "flexible" group (p. <.O5). There were no significant interactions. The first 3 factors appear to operate together additively, with sex most important, parental fixation-prone-ness next, and stress least effective in producing increases in alcohol consumption. The results regarding the effects of stress on consumption are not clearly due to stress alone, since stressed animals were simultaneously food-deprived and, therefore, part of the increase in alcohol intake may have been caused by their need for additional calories.