Effects of estradiol treatment on voluntary and forced alcohol consumption in male rats.

Estrogens have been related to alcohol as a dependent variable, but scarcely as a causal variable, that affects the alcohol consumption. The scope of the present work was to study the effect of estrogens on both the amount and the pattern of alcohol consumption. Male Wistar rats were individually exposed to forced alcohol consumption (FAC) and voluntary alcohol consumption (VAC) in each of the following four periods: precastration (PreC), postcastration (PosC) or post-sham castration, estradiol (E) treatment (5 microg of estradiol benzoate/day/rat) and postestradiol (PosE). Estrogenic treatment reduced significantly the alcohol consumption with respect to the PreC and PosE periods in castrated (C) males during VAC. E treatment showed the lowest value of alcohol intake in FAC, but differences were significant only with respect to PreC regardless of the male gonadal condition. E treatment decreased food intake regardless of the male gonadal condition in both FAC and VAC. Castration and E treatment modified differentially the patterns of alcohol consumption depending on the volitive characteristics of alcohol intake. Castration reduced the size of the licking rates without affecting the number of drinking bouts in FAC. This pattern was maintained in the E and PosE periods of C males. Castration did not affect the pattern of alcohol consumption in VAC, but estrogen reduced both the bout size and the number of bouts during the day, which gave an additional support to the inhibitory effect of estrogens on VAC. Results are discussed in terms of a possible inhibitory action of estrogens on the opioid system, which possibly reduces the rewarding properties of alcohol.