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Sent: August 10, 2011 16:40
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Subject: BRAIN ELECTRICAL ACTIVITY SPURS INSULATION OF BRAIN'S WIRING

U.S. Department of Health and Human Services 
NATIONAL INSTITUTES OF HEALTH NIH News 
Eunice Kennedy Shriver National Institute of Child Health and Human
Development (NICHD) <http://www.nichd.nih.gov/>
For Immediate Release: Wednesday, August 10, 2011

CONTACT: Robert Bock, Marianne Glass Miller, 301-496-5133,
<e-mail:[log in to unmask]>

BRAIN ELECTRICAL ACTIVITY SPURS INSULATION OF BRAIN'S WIRING
NIH study identifies trigger that speeds brain cell communication

Researchers at the National Institutes of Health have discovered in mice a
molecular trigger that initiates myelination, the process by which brain
cell networks are reinforced with an insulating material called myelin that
speeds their ability to transmit messages.

The myelination process is an essential part of brain development.  Myelin
formation is necessary for brain cells to communicate and it may contribute
to development of skills and learning.

The researchers showed that an electrical signal passing through a brain
cell (neuron) results in the brain cell releasing the molecule glutamate.
Glutamate, in turn, triggers another type of brain cell, called an
oligodendrocyte, to form a point of contact with the neuron.  Signals
transmitted through this contact point stimulate the oligodendrocyte to make
myelin protein and begin the process of myelination.  In this process, the
oligodendrocyte wraps myelin around axons -- the long, cable-like
projections that extend from each neuron.  The myelination process is
analogous to wrapping electrical tape around bare wires.

Electrical signals transmitted from one neuron to the next are a basic form
of communication in the brain.  The myelin layers that oligodendrocytes wrap
around neurons boost these signals so that they travel 50 times faster than
before.

The study was conducted by Hiroaki Wake, Philip R. Lee, and R. Douglas
Fields of the Nervous System Development and Plasticity Section of the NIH's
Eunice Kennedy Shriver National Institute of Child Health and Human
Development (NICHD).  Their findings appear online in Science Express.

"Insulation begins to form on axons in the late stages of fetal development,
but the process continues through childhood, adolescence, and into early
adulthood," said Dr. Fields, the study's senior author.  "For example,
infants cannot hold up their heads or walk until the appropriate motor axons
become myelinated, and the frontal lobes of the brain, responsible for
judgment and higher-level complex reasoning, are not fully myelinated until
the early twenties."

Understanding how oligodendrocytes generate and help repair myelin could
provide insight into how only the appropriate axons in the brain become
insulated during development as people acquire skills, with the eventual
goal of helping them do so more efficiently, Dr. Fields explained.
Similarly, understanding the myelination process could lead to insights into
disorders like multiple sclerosis, in which myelin is either damaged or
destroyed.  Moreover, understanding myelination may allow researchers to
speed myelination -- and repair -- of axons recovering from injury.

Throughout the brain, oligodendrocytes and neurons exist side by side.  The
researchers placed mouse nerve cells and myelin-making oligodendrocytes
together in a dish and stimulated the nerve cells with electrical pulses.
After three weeks, they found that the nerve cells were wrapped in a myelin
covering.

In a separate culture of neurons and oligodendrocytes, the researchers
blocked the release of the molecule glutamate, a neurotransmitter.
Neurotransmitters make it possible for signals to pass between cells.  When
glutamate release was blocked, very little myelin coating formed.  Further
experiments showed that after the electrical pulses and the release of
glutamate, nerve cells and the neighboring oligodendrocytes began sending
chemical signals back and forth.  Then the oligodendrocytes started to make
the protein used to form the myelin sheath.  Specifically, receptors on the
cell membrane of oligodendrocytes detect glutamate released by the axon, and
this triggers the formation of what the researchers termed specialized
adhesive signaling junctions -- points of contact between oligodendrocytes
and axons that enable signals to be passed between the cells.  Then the
oligodentrocytes began depositing myelin on electrically active axons, but
not on axons that were not electrically active.

"This shows that axons that are transmitting electrical signals will become
preferentially insulated by myelin," Dr. Fields said.  

In a previous study, Dr. Fields and his coauthors found that electrical
activity in neurons stimulates other cells, called astrocytes, that also are
involved in the myelination process
<http://www.nichd.nih.gov/news/releases/electrical_impulses.cfm>. 

The NICHD sponsors research on development, before and after birth;
maternal, child, and family health; reproductive biology and population
issues; and medical rehabilitation.  For more information, visit the
Institute's website at <http://www.nichd.nih.gov/>. 
 
About the National Institutes of Health (NIH): NIH, the nation's medical
research agency, includes 27 Institutes and Centers and is a component of
the U.S. Department of Health and Human Services. NIH is the primary federal
agency conducting and supporting basic, clinical, and translational medical
research, and is investigating the causes, treatments, and cures for both
common and rare diseases. For more information about NIH and its programs,
visit <www.nih.gov>.
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IMAGE INFORMATION:
URL -
<http://www.nichd.nih.gov/news/releases/images/081011-Myelin_Formation.jpg>
Caption - Electrical signals transmitted from one neuron to the next are a
basic form of communication in the brain.  These signals travel along
projections, called axons, which extend from neurons.  Oligodendrocytes wrap
axons in an insulating material, called myelin, that speeds up the
electrical signals.  The myelination process is essential for normal nervous
system function and it may contribute to learning and skill development.  In
this study, NIH researchers found a trigger for the myelination process.
When electrical signals travel down an axon, the axon releases a molecule
called glutamate.  Glutamate stimulates the oligodendrocyte to form a point
of contact with the axon through which it receives axon signals.  The
oligodendrocytes then begin wrapping the myelin covering around the axons.
Alt tag - Myelin formation

  
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