Drinking Like a Girl

6 January 2006 (All day)

Pound for pound, females appear to be better at holding their liquor than males, and now scientists may have found one reason why. A new study in rats suggests that hormone levels in the brain may mediate alcohol's potency, giving females a leg up at certain times during their hormonal cycle.

The gender gap in alcohol metabolism is no secret. Women metabolize alcohol more slowly than men and that makes them more susceptible to alcoholic liver disease, heart muscle damage, and brain damage. Rat studies suggest that males and females in their teenage years are equally affected by the equivalent of a stiff drink, but females are less sensitive to alcohol's sedative powers when they become adults. And, given an open "tab," female rats drink more than the males, but their consumption varies across their hormonal cycle.

These findings suggest that hormone levels may mediate alcohol's potency, say H. Scott Swartzwelder of Duke University Medical Center in Durham, North Carolina. To examine this link more closely, Swartzwelder and colleagues studied the sedative effects of alcohol by injecting the equivalent of about 20 drinks of alcohol into adolescent and adult rats of both genders and throughout the females' estrous cycle. The researchers then observed how long it took for the rats to stand up on all four feet from a prone position.

The team found that although no differences in alcohol behavior were found between male and female adolescent rats, adult females were generally better than males at getting upright after they'd had a few. But the estrous cycle made a significant difference. During their estrous peak, the females took 10% longer to get up than before and after the cycle's onset.

Then, by analyzing the rats' brains, the team got another measure of the gender difference. When tipsy females were at their most nimble, during their pre- and postestrous states, the ethanol had 10% less impact on neurotransmitter activity than it did on the drunken males' neurotransmitters. These results suggest that the gender gap in alcohol behavior may have to do with how hormones play into both gender-related and estrous cycle-related changes in central nervous system excitability, the team reports this month in Alcoholism: Clinical and Experimental Research.

"This is a great piece of work," says neuroscientist Marisa Silveri of Harvard Medical School in Boston, Massachusetts. Because alcohol may affect females differently at different times of the month, she notes, women should pay especially close attention to their menstrual cycles when judging when to say when.

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