Ovarian Hormones Contribute to High Levels of Binge-Like Drinking by Female Mice - PubMed (original) (raw)

Ovarian Hormones Contribute to High Levels of Binge-Like Drinking by Female Mice

Rosalba Satta et al. Alcohol Clin Exp Res. 2018 Feb.

Abstract

Background: Recently, the incidence of binge drinking by women has increased. Binge drinking is detrimental to women's health, yet the biological mechanisms that promote excessive drinking by women are not well understood. One method of assessing binge-like ethanol (EtOH) consumption in mice is the drinking in the dark (DID) test, in which mice drink sufficient EtOH to achieve intoxication. In this study, we directly compared male, female, and ovariectomized (OVX) mice for DID and tested whether 17β-estradiol (E2) contributes to DID. We also measured whether DID varies throughout the estrous cycle and whether repeated intermittent DID impacts the estrous cycle.

Methods: Male, female, and OVX C57BL/6J mice were tested for DID for 2 hours per day on days 1 to 3 and for 4 hours on day 4 using a single bottle containing 20% EtOH. To measure the effects of E2 on DID, OVX mice were treated with estradiol benzoate (EB) or vehicle daily starting 2 weeks prior to the drinking test and throughout the DID procedure. In a separate group of experiments, EtOH consumption and estrous cycle phase were measured in freely cycling mice that were drinking EtOH or water 5 days per week for 2 or 6 weeks.

Results: Female mice consumed more EtOH than male and OVX mice. Treatment with EB increased EtOH consumption by OVX mice compared with vehicle-treated controls. However, EtOH intake did not vary across the estrous cycle, nor did long-term DID alter the estrous cycle.

Conclusions: These results demonstrate that ovarian hormones, specifically E2, contribute to increased EtOH consumption by female mice in the DID test. Although ovarian hormones contribute to this behavior, EtOH consumption is not affected by estrous cycle phase in freely cycling mice. This study provides a framework for understanding the factors that contribute to binge drinking in females.

Keywords: Alcohol; Binge Drinking; Estrogen; Female; Sex Differences.

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Figures

Fig. 1

Females consume more ethanol (EtOH) in the drinking in the dark test than males and ovariectomized (OVX) mice. (A) EtOH consumed (g/kg) during 2-hour drinking sessions on days 1–4. (B) EtOH intake (g/kg) during the 4-hour session on day 4. **p < 0.01 between males and females and between females and OVX, n = 16 per group (C) Blood EtOH concentrations (BECs, mg/dL) at the end of the 4-hour drinking session on day 4, n = 8 per group. *p < 0.05 between males and OVX and **p < 0.01 between females and OVX. Data are presented as mean ± SEM.

Fig. 2

17β-estradiol benzoate (EB) increases binge-like EtOH drinking in ovariectomized (OVX) mice. (A) Timeline of the experiment. EB injections were given daily for two weeks prior to testing drinking and before each drinking session (B) EtOH intake (g/kg) during each 2-hour drinking session from days 1–4 in OVX mice treated with vehicle (VEH) or EB. (C) EtOH consumed during the 4-hour session on day 4, n = 10–11 per group. (D) Blood EtOH concentrations (BECs, mg/dL) after the 4-hour session on day 4, n = 4–6 per group. **p < 0.01. Data are presented as mean ± SEM.

Fig. 3

Ethanol (EtOH) intake in the drinking in the dark procedure is not altered during the estrous cycle. Representative bright field microscopic images (10x magnification) of vaginal smears are shown from mice in proestrus (A), estrus (B), metestrus (C) and diestrus (D). (E) Average EtOH intake (g/kg) during 2-hour daily sessions at each stage of the cycle. Cycle stage information was collected from 10 mice, 5 days a week for 6 weeks. Proestrus, n = 44; Estrus, n =104; Metestrus, n =14; Diestrus, n = 57. (F) Average EtOH intake (g/kg) during 4-hour daily sessions at each stage of the cycle by 8 mice, 5 days a week for 2 weeks. Proestrus, n = 13; Estrus, n = 40; Metestrus, n = 7; Diestrus, n = 18. (G) Average EtOH intake (g/kg) in the last two hours of the 4-hour drinking session shown in (F). All data are shown as means ± SEM.

Fig. 4

Ethanol (EtOH) drinking during drinking in the dark does not affect the length and pattern of the estrous cycle. (A) Length of the estrous cycle and (B) number of days spent in estrus and diestrus in mice drinking 20% ETOH or water in the DID procedure for 2 hours daily, 5 days per week for 6 weeks. Data are expressed as mean ± SEM from n =10 mice per group.

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Ovarian Hormones Contribute to High Levels of Binge-Like Drinking by Female Mice - PubMed (original) (raw)