BRAIN MAKES POT-LIKE CHEMICALS

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BRAIN MAKES POT-LIKE CHEMICALS

Researchers Study Neurons

SAN JOSE, Calif. - Mother Nature created a way to ``tune in, turn on''
long before pot-smokers rolled their first joint, Stanford scientists
have found.

Eavesdropping on the conversations between brain cells, the research
team found that neurons make their own marijuana-like chemicals called
cannabinoids, which indirectly alter the way information is received
and filtered.

When the chemicals are released, ``neurons have a harder time deciding
which are the relevant things to pay attention to,'' said investigator
John R. Huguenard, associate professor of neurology and neurological
sciences at Stanford University School of Medicine.

For a long time, scientists thought that marijuana altered the mind in
a messy and random way.

Now they've identified an elegant modus operandi. It adds to a growing
body of research that explains the mechanism behind getting ``high.''
Marijuana mimics the cannabinoids made naturally by our brain --
chemicals that influence a smorgasbord of body functions including
movement, thought and perception.

The research sheds light on a powerful neurochemical system. In their
Stanford lab, Huguenard and colleagues David Prince and Alberto Bacci
injected electric current into rat brain cells, then watched the
chatter between the brain's two major types of cells.

When overly excited, one type of neuron releases cannabinoids, which
create a calming effect, they found. In effect, the brain cell drugs
itself.

But this mellowed-out cell falls down on its job, which is to filter
the flow of information rushing into a second type of cell.

Without a good filter, the researchers think, this second neuron is
flooded with sensory information that affects memory, perception, mood
and movement.

Something very similar happens with marijuana use, the scientists
believe.

In an accident of nature and chemistry, the compounds in pot are
shaped similarly and trigger similar effects.

``Marijuana use . . . affects the way we think,'' said Huguenard. The
new research shows that ``part of that is because of changes in the
way our brain cells receive incoming information, like sensory
information or memories or emotion.''

Because so much information is always flowing into the brain, ``each
neuron has to make a decision based on the signals it gets,'' he said.
``They have to make sense of it . . . and decide what's relevant.''

``Marijuana loosens a na
tural filter that exists in neurons, so they
tend to be flooded with information,'' Huguenard said.

The research is published in today's issue of the journal Nature.