ADOLESCENT RATS MORE RATTLED BY MARIJUANA

DURHAM -- Marijuana may inhibit memory and learning -- at least
temporarily -- to a greater degree in adolescents than in adults,
according to a study by researchers at Duke University and the Durham
Veterans Affairs Medical Center.

The research findings, published last week in the print edition of
the journal Pharmacology, Biochemistry and Behavior and in an advance
online edition in March, reported effects of tetrahydrocannabinol,
the active ingredient in marijuana, in a series of experiments last
year using rats. Half of the nearly 200 rats were adolescent and half
adult. All were male. When given THC, the adolescent rats took longer
than the adults to remember where to swim in a shallow pool about 4
feet across to a small submerged platform. When the platform was
moved to a new location and raised above the water where the rats
could see it, the younger ones still took longer to reach it. In the
memory test, adolescent rats took 64 percent longer than their elders
to reach the platform. At higher concentrations of THC, the age
difference in performance fell to 47 percent, as all the rats became
more disoriented, the researchers said.

The effect disappeared when the rats were no longer under the
influence of THC. Control rats that were not given THC learned to
swim to the platform easily, said Young Ma Cha, the study's lead author.

An area of the brain similar in both rats and humans called the
hippocampus is associated with spatial learning and memory. The
researchers hypothesize that the effect of THC on it may be similar,
said Scott Swartzwelder, a professor of psychiatry at Duke and the
Durham Veterans Affairs Medical Center who was the study's senior author.

"The whole goal of this research program is to better inform the
public, to have as a point of discussion something more than a slogan
or scare tactics," he said.

People's brains continue to develop and change throughout life, but
young people's learning is foundational, the researchers said. "I
think the important thing is not to go too far in the sense of
looking at 'How many joints is my son or daughter going to smoke
before he or she becomes seriously impaired at studying?' " said Cha.
"The idea is to look at the overall picture. Our younger rats, who
model human adolescents, are showing serious impairment. That should
definitely send a red flag to anyone who's thinking of using THC."

A representative of the National Organization for the Reform of
Marijuana Laws in Washington, D.C., said the study appeared to turn
little if any new ground, since the effect of THC on cognitive
performance and even brain scans of human subjects including
adolescents has been researched extensively for decades.

Those studies consistently have found no significant long-term
impairment, said Paul Armentano, a senior policy analyst with NORML.
"Certainly, NORML does not believe, as any responsible organization,
that the use of intoxicating substances, including marijuana, is a
good idea for children to engage in," Armentano added.

Neither would the organization dispute that marijuana affects memory
and learning while people are under its effect, he said. Other
researchers participating in the study include Duke and VA
researchers Aaron White, Cynthia Kuhn and Wilkie A. Wilson.

Now they're doing similar experiments with female rats, Cha and
Swartzwelder said.