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First Glimpse of Mechanistic Explanation for Placebo Effect

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    NHNE News List Current Members: 1031 Subscribe/unsubscribe/archive info at the bottom of this message. ... PLACEBOS EFFECT REVEALED IN CALMED BRAIN CELLS By
    Message 1 of 1 , May 19, 2004
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      PLACEBOS EFFECT REVEALED IN CALMED BRAIN CELLS
      By Andy Coghlan
      New Scientist
      May 16, 2004

      http://www.newscientist.com/news/news.jsp?id=ns99994996

      Detailed scans of brain cells in Parkinson's disease patients have revealed
      the action of the placebo effect on an unprecedented scale.

      "It's the first time we've seen it at the single neuron level," says
      Fabrizio Benedetti, head of the team which conducted the experiments at the
      University of Turin Medical School in Italy.

      When the patients in the study received a simple salt solution, their
      neurons responded in just the same way as when they had earlier received a
      drug which eased their symptoms.

      "The research provides further evidence for a physiological underpinning for
      the placebo effect," says Jon Stoessl, at the University of British Columbia
      in Vancouver, Canada. His team demonstrated in 2001 that placebos can
      relieve symptoms by raising brain levels of dopamine, a beneficial
      neurotransmitter.

      "We suggest that the changes we ourselves observed are also induced by
      release of dopamine," says Benedetti.

      Abnormal firing

      Parkinson's patients suffer from a lack of dopamine, meaning that brain
      cells in a region called the subthalamic nucleus firing in abnormal bursts.
      This triggers the familiar symptoms of muscle rigidity, tremors and slowness
      of movement.

      Drugs which mimic dopamine, such as L-Dopa and apomorphine, can block
      abnormal firing. But now, Benedetti has shown that a simple saline solution
      did the same.

      First, he "pre-conditioned" the patients by giving them three doses of
      apomorphine. Then he surgically implanted electrodes into each patient's
      subthalamic nucleus, each carrying sensors to monitor the firing activity of
      around 100 individual neurons.

      During the surgery, for which the patients remained awake, he also
      administered the placebo. He found that it induced the same calming effect
      on neurons as the apomorphine.

      Residual traces of apomorphine cannot explain the findings, he says:
      "Apomorphine effects only last for one hour, and the last apomorphine dose
      they received was 24 hours before the operation."

      Cognitive vs conditioning

      He suggest two possible explanations. The first is the "cognitive"
      hypothesis, where the physiological effects are triggered by the patient's
      expectation of benefits.

      The second is the classic "conditioning" response. This was discovered in
      1889 by the Russian psychologist, Ivan Pavlov, who found conditioning could
      induce dogs to salivate for food at the sound of a bell. "The context around
      the therapy could induce such a response," says Benedetti.

      In his latest experiments, Benedetti is investigating whether the brain
      cells react to placebos in "naive" Parkinson's patients, who have not first
      been conditioned with genuine drugs.

      "It's a logical next step," says Edzard Ernst, professor of complementary
      and alternative medicine at the University of Exeter, Devon, UK. He
      describes the new work as "one of the first glimpses of a mechanistic
      explanation for the placebo effect".

      Journal reference: Nature Neuroscience: (DOI: 10.1038/nn1250)

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      PLACEBOS FIGHT DEPRESSION AS WELL AS DRUGS (5/8/2002):
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      THE NOCEBO EFFECT: PLACEBO'S EVIL TWIN (5/2/2002):
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      THE PLACEBO EFFECT: THE POWER OF NOTHING (5/26/2001):
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