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Natural High Extinguishes Bad Memories in Brain
Publication date: July 31, 2002
Source: Reuters
Author: Patricia Reaney
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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Distributed without profit to those who have expressed a prior interest in
receiving the included information for research and educational purposes.
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