16383Mice overcome fear, depression with natural Prozac
- Oct 10 3:33 PMMice overcome fear, depression with natural Prozac
WASHINGTON, Oct. 8, 2008
The brain can produce antidepressants with
the right signal, a finding that suggests that
meditating, or going to your "happy place,"
truly works, scientists reported on Wednesday.
Mice forced to swim endlessly until they
surrendered and just floated, waiting to drown,
could be conditioned to regain their will to
live when a tone they associated with safety
The experiment suggests that there are good
ways to teach people this skill, and points
to new routes for developing better antidepressants,
said Dr. Eric Kandel of the Howard Hughes Medical
Institute and Columbia University in New York,
who led the research.
"The happy place works. This is like going to
the country," Kandel said in a telephone interview.
Writing in the journal Neuron, Kandel's team
said they used classical conditioning to train
mice. They had already conditioned some mice to
fear a neutral tone by playing the sound when
they shocked the animals' paws. After a while,
the tone itself creates fear.
"It scares the hell out of the animal,"
They decided to reverse the study -- they
played the tone when they were not shocking
the mice. "It learned that the only time it
was really safe is when the tone comes on," Kandel said.
To make a mouse depressed, they used a method favored by drug
companies called learned helplessness.
"You put an animal into a pool of water and
it can't get out. It gives up and it stops
swimming and it just floats," Kandel said.
"When you give the animal an antidepressant,
it starts swimming again. When we played the
tone, it started to swim again just as it did
with the antidepressant."
Further experiments showed the tone and an
antidepressant drug worked synergistically, he said.
When they looked at the brains of their mice,
they saw using the conditioned "safety" tone
activated a different pathway than the drugs did.
It affected dopamine, while antidepressants
work on serotonin. Both are message-carrying
molecules called neurotransmitters.
The conditioning also affected a compound
called brain-derived neurotrophic factor or
BDNF -- which helps nourish and encourages
the growth of brain cells.
The learned safety did not affect serotonin.
Mice conditioned by the "safety" tone also had
more newborn brain cells in the dentate gyrus,
a part of the brain linked with learning and
When Kandel's team used radiation to slow the
birth of new cells in the dentate gyrus, the
effects of learned safety and of antidepressants
Kandel noted that antidepressant drugs appear
to work, in part, by encouraging the growth of
new brain cells -- as does psychotherapy.
"Learning involves alterations in the brain and
gene expression," Kandel said. "Psychotherapy
is only a form of learning."
This shows how effective psychotherapy, meditation
and other stress-reduction tools may be, and it
could help in the design of new drugs, Kandel said.
"This opens up new pathways that may profitable,"
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