| Alcohol's Effects
On Fetal Brain Revealed |
By Merritt McKinney
NEW YORK, (Reuters
Health) -- For the first time, researchers have
discovered how drinking alcohol during pregnancy damages the
brain of a
fetus.
In the United States, about 1 out of every 1,000 children
is born with
fetal alcohol syndrome, which can cause a range of problems,
including
learning and memory problems, hyperactivity, stunted growth,
and an
abnormally small head. According to a report in the February
11th issue of
the journal Science, getting drunk just one time during the final
3 months
of pregnancy may be enough to cause brain damage in a fetus.
"This is the first time we've had an understanding of
the mechanism by
which alcohol can damage the fetal brain," one of the study's
authors, Dr.
John W. Olney, of Washington University School of Medicine in
St. Louis,
Missouri, told Reuters Health in an interview. "It's a mechanism
that
involves interfering in the basic transmitter systems in the
brain, which
literally drives the nerve cells to commit suicide."
Even though this damage appears most likely to occur during
the third
trimester, it is still probably not a good idea to drink at any
time during
pregnancy, since the physical deformities caused by fetal alcohol
syndrome
may occur early in pregnancy, Olney said.
In the study, researchers exposed 7-day-old rats to ethanol,
the alcohol in
beer, wine and hard liquor. The investigators chose this age
since the
brain is thought to be most sensitive to the effects of alcohol
during a
period called synaptogenesis, when the brain develops rapidly.
In rats,
this growth spurt occurs after being born, while in people it
begins in the
third trimester of pregnancy and continues into early childhood.
In these experiments, the researchers found that exposing
rats to a high
level of alcohol for several hours during this crucial period
of brain
development caused large number of nerve cells in several important
parts
of the brain to die. In his comments to Reuters Health, Olney
said that it
is difficult to say precisely how much alcohol would cause the
same amount
of damage in humans. He did note, however, that just one episode
of
drunkenness during the third trimester, when brain cells are
developing
rapidly, would be enough to damage the brain of a fetus.
The investigators determined that alcohol affects two brain
chemicals,
glutamate and GABA, which help different parts of the brain communicate
with each other. "It kind of does a double whammy,"
he said. "It hits the
brain with both mechanisms."
Olney also believes that the variety of symptoms seen in fetal
alcohol
syndrome is due to the timing of alcohol exposure. Alcohol's
effects on the
fetal brain depend on the stage of development of the brain when
the
exposure occurs.
Several types of medications that also act on these brain
chemicals are
often used as sedatives, anesthetics and antiseizure treatments
during
pregnancy and early childhood, according to Olney. Based on the
results of
the study, the safety of using these drugs during the third trimester
and
early childhood should be re-evaluated, he said.
The researcher plans to continue to study the results of alcohol
exposure
on rats as they mature, with the goal of discovering the link
between
damage to certain parts of the brain and problems in the adult
animal.
SOURCE: Science 2000;287:947-948, 1056-1060
|
