Ethanol consumption in the female Long–Evans rat:☆

Abstract 

The examination of various gonadal hormone manipulations on ethanol intake in human subjects and in rodent models has resulted in disparate findings. In the present study, we examined the effects of ovariectomy and subsequent estradiol (E₂) replacement on ethanol intake in a within-subject design, as well as assessed the relevance of reproductive status on the efficacy of an E₂ stimulus in eliciting consumption. Female Long–Evans rats (n = 24) were given access to 10% ethanol and water in a continuous-access paradigm. After establishment of baseline intake values, rats were divided into four groups: sham/placebo (Shm+P), sham/estradiol (Shm+E₂), ovariectomized/placebo (Ovx+P), and ovariectomized/estradiol (Ovx+E₂). Rats in the Ovx+P group were found to have a large and permanent decline in ethanol intake that persisted more than 3 months postsurgery. Administration of E₂ to Ovx+E₂ rats was associated with restoration of ethanol consumption to baseline levels. When Shm+E₂ and Ovx+E₂ groups were compared, reproductive status was found to be a determining factor in the efficacy of E₂ to elicit ethanol intake. Together, these findings provide evidence that ovarian hormones, particularly estradiol, exert activational effects on estrogen-responsive substrates to modulate ethanol consumption in the adult female rat.

Keywords:  Ethanol self-administration, Continuous access, Female rat, Ovariectomy, Estradiol replacement