By Alfa · Sep 18, 2004 ·
  1. Alfa

    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

    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

    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.

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