Sex differences and hormonal modulation of ethanol-enhanced risk taking in rats.

BACKGROUND

Ethanol (EtOH) intake correlates with increased risk-taking, and sex differences exist in both EtOH use and risk-taking in humans and rats. However, the interaction of sex and gonadal hormones to affect risk-taking under the influence of EtOH has not been determined. This was the focus of the current study.

METHODS

Adult Long-Evans rats (n=18 males and females) were gonadectomized and received hormone replacement at physiologic levels or blank implants (n=7-9/group). Risk-taking was assessed with probability discounting, requiring rats to choose between a small/certain reward and a large/uncertain reward delivered with decreasing probability throughout each daily session. Before testing, rats received saline or EtOH (0.5 or 1.0g/kg) ip.

RESULTS

In males, EtOH increased preference for the large/uncertain reward lever (F=10.462, p<0.05). However, there was no effect of EtOH on lever preference in females (F=0.914, p>0.05). At baseline, ORCHX+T males showed a greater preference for the large/uncertain reward lever then ORCHX males (F=13.805, p<0.05). In females only, EtOH decreased choice latency relative to baseline (F=7.25, p<0.05). EtOH decreased loss sensitivity in both sexes, with all rats exhibiting decreased lose-shift ratios (males: F=5.10, p<0.05; females F=4.37, p<0.05).

CONCLUSIONS

These results show that EtOH, sex, and hormones interact to influence decision making. EtOH increases risk taking in males, but not in females. However, EtOH selectively decreases choice latency in females, and decreases loss sensitivity in both sexes. These findings are relevant to understanding human behavior, particularly in adolescents who experience increased hormone levels and often drink EtOH and engage in risky behavior.