快猫短视频

ALCOHOL鈥橲 legendary sedative effects may be caused by a brain steroid derived
from progesterone that damps down anxiety. This could help explain why alcohol
makes people feel so relaxed, and why men and women react to alcohol
differently.

It only takes a few drinking sessions for revellers to get acquainted with
alcohol鈥檚 effects. 快猫短视频s, though, have had a harder time figuring out
exactly how the drug works on the brain. Alcohol appears to interact with two
brain receptors, one of which, the GABA receptor, is exploited by tranquillisers
such as Valium. But it is not clear exactly how alcohol interacts with this
receptor.

Animal studies show that stress increases levels of the brain steroid
allopregnanolone, which acts on the GABA receptor to reduce anxiety, says Leslie
Morrow of the University of North Carolina in Chapel Hill. Because alcohol
triggers the release of stress hormones like corticosterone, and progesterone,
from which allopregnanolone is derived, Morrow鈥檚 team suspected that drinking
might also increase levels of the steroid.

To find out, the researchers gave rats moderate doses of ethanol roughly
equivalent to the amount of booze someone might consume at a cocktail party.
When they removed each animal鈥檚 cerebral cortex after 20 minutes, the rats given
alcohol showed dramatic rises in allopregnanolone levels compared to rats given
saline.

Was the steroid responsible for alcohol鈥檚 sedative effect? Morrow treated
rats with a drug called finasteride, which blocks the formation of
allopregnanolone from progesterone, before giving them another tipple. Alcohol
usually lowers electrical activity in a number of areas in the brain, but
finasteride prevented this, indicating that allopregnanolone does play a role in
the relaxing effects of alcohol.

Morrow is thrilled by the results. 鈥淲e think that allopregnanolone is very
important for the anticonvulsant and sedative effects of alcohol.鈥� Perhaps women
need to drink less to get the rewarding effects of alcohol because they
naturally have higher levels of the steroid, she says. That could explain why
women are less likely to become alcoholics than men.

鈥淚t鈥檚 an exciting finding,鈥� agrees George Koob at the Scripps Research
Institute in La Jolla, California. Koob has previously shown that female rats
drink more ethanol during the phase in their reproductive cycle when
progesterone levels are low. An important future question will be what role
neuroactive steroids play in vulnerability to alcoholism, and not just acute
intoxication, he says.