X-Message-Number: 13997
Date: Fri, 23 Jun 2000 20:38:35 -0700
From: Bryan Hall <>
Subject: Protein Plays Role in Long-Term Memory

NEW YORK (Reuters Health) - A protein in the brain with suspected links
to the circadian clock appears to play a role in long-term memory,
according to findings published in the June 23rd issue of Science.

If further study shows that the protein, called NPAS2, is also involved
in the body's internal clock, then it could reveal a connection between
circadian rhythm and complex brain functions such as learning and

``Behavior of organisms, including learning and memory, is determined by
both environmental as well as genetic influences that
are largely unknown,'' Dr. Joseph A. Garcia of the University of Texas
Southwestern Medical Center in Dallas told Reuters
Health. Garcia led the team of researchers that studied the behavior of
mice with and without the protein called NPAS2,
which regulates specific genes in the brain.

``Mice that lack normal NPAS2 have decreased long-term memory for
sights, places, smell, and sound associated with an
aversive event,'' explained Garcia. ``These results may have
implications in humans for learning and memory as well as for
certain psychiatric disorders including autism, depression, and mental

The researchers trained mice with and without the protein by giving them
a mild electric shock immediately after they heard a
specific sound. When the mice were placed in the same environment 24
hours later to test their memory, those missing
NPAS2 showed significantly less ``freezing'' behavior--holding stock
still, an indication of fear--than those who had the

There were no differences between the two groups in the test given 30
minutes after training, indicating that short-term
memory wasn't affected by the protein.

In another test to see if the mice remembered the sound that cued the
electric shock, the researchers put the animals in a new
environment, but used the same sound. Before the sound was played, the
two groups of mice behaved similarly, but after it,
the mice missing NPAS2 again showed less fear behavior, indicating that
they didn't remember the sound.

``NPAS2 appears to be required for the processing of complex sensory
information,'' the researchers conclude. The protein is
found in all vertebrates, they note, and only in cells of the nervous

In the report, Garcia's team note that the closest relative of NPAS2 is
the CLOCK protein, the ``master regulator of circadian
rhythm.'' Previous studies showed that conditioned fear can affect
circadian rhythm in lab animals. The findings of this study
suggest that NPAS2 may be a link between the learning parts of the brain
and those involved in the body clock, which
regulates sleep-wake cycles, hormone secretion, and various other body
functions that follow daily rhythms.

If further study shows that NPAS2 does play a role in circadian rhythm,
the researchers speculate, then it may mean that the
rhythmic expression of genes play a role in the brain's ability to
perform complex tasks, such as learning and laying down
memories. Such a finding may lead to new ways to treat learning
disorders and some psychiatric diseases that involve these
brain circuits.

Full story at http://dailynews.yahoo.com/h/nm/20000623/hl/protein_2.html

-Bryan Hall

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