NATURAL HIGH EXTINGUISHES BAD MEMORIES IN BRAIN

LONDON (Reuters) - Feel-good chemicals in the brain, similar to the active
ingredient in cannabis, can wipe out bad memories, German scientists said in
a finding that could lead to new treatments for anxiety disorders and
phobias.

Researchers at the Max Planck Institute of Psychiatry in Munich have shown
that natural chemicals in the brain similar to THC, the active ingredient in
marijuana which produces the high, dampen nerve cell action and wipe out
unpleasant memories.

THC, or tetrahydrocannabinol, and similar molecules in the brain known as
cannabinoids bind to the brain's chemical receptors, and can create a
feeling of euphoria.

Cannabis and hashish, which contain THC, have been used for centuries for
medicinal and recreational purposes.

Dr. Beat Lutz and his team created transgenic, or genetically modified, mice
without a cannabinoid receptor. When they conditioned them to associate a
musical tone with an electric shock, the mice produced a fear reaction, and
continued to react even when the tone was not followed by a shock, Lutz
said.

Normal mice quickly stopped reacting to the tone once it was not associated
with a shock, but the genetically modified mice without the cannabinoid
receptor took much longer to forget their fear.

Lutz and his team, whose research is published in the science journal
Nature, also showed that blocking the receptor in normal mice prevented the
animals from forgetting the painful memory.

When the scientists studied an almond shaped area of the brain called the
amygdala, central to storing memory and fear, in transgenic and normal mice
they discovered it was flooded with natural chemicals, or endocannabinoids,
when the mice were gradually forgetting the learned response to the shock.

Lutz believes the chemicals help to wipe out the fear or memory of the
unpleasant response by binding to the cannabinoid receptors, he said on
Wednesday.

Smoking cannabis would not produce the same effect in humans, Lutz said,
because it overflows the brain and is not specific enough to extinguish the
unpleasant memory.

Lutz and his team think drugs that target specific enzymes to boost
cannabinoids in the amygdala could help people suffering from panic attacks
and fear-related memories.

"The finding that the endocannabinoids contribute to extinction raises the
possibility that drugs that target these molecules and their receptors could
be useful new treatments for anxiety disorders," Pankaj Sah, of the
Australian National University in Canberra, said in a commentary in Nature.

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