X-Message-Number: 11909
Date: Sun, 06 Jun 1999 18:27:26 -0400
From: Jan Coetzee <>
Subject: Aging alone not

Contact: Martin Sarter
    Ohio State University

    Aging alone does not affect brain system related to
    memory loss

    Columbus, Ohio -- A new study in rats suggests that aging by itself
may not affect
    brain systems responsible for important aspects of learning and
memory. However,
    the research found that the combination of old age and pre-existing
brain pathology
    led to serious problems in a brain system that is crucial for normal
cognitive abilities.

    The findings have important implications for researchers studying
Alzheimer's disease
    and other forms of dementia in humans, said Martin Sarter, co-author
of the study and
    a professor of psychology at Ohio State University.

    "The aging of the brain may not be sufficient to produce seriously
detrimental effects
    in humans," Sarter said. "It may be that only people who have a
problem in important
    brain systems who will suffer dementia as they get older."

    Sarter conducted the study with John Bruno, also a professor of
psychology at Ohio
    State, and James Fadel, a former graduate student. Sarter presented
their results June
    6 in Denver, Colo. at the annual meeting of the American
Psychological Society. The
    study was also published in the May 1999 issue of the journal

    In the study, the researchers trained rats to associate darkness
with the appearance of
    food they liked. They did this because darkness would then stimulate
the cholinergic
    system -- the brain system that involves memory functions and is
associated with
    Alzheimer's disease and other forms of dementia. In order to further
stimulate the
    cholinergic system, rats also received a drug to allow this system
to react more
    readily to stimulation.

    To measure the reaction of the rats' cholinergic systems to the
stimulus of darkness
    and food, the researchers examined the release of acetylcholine
(ACh), the crucial
    brain chemical that works within this system.

    The researchers examined both young adult rats (four to seven months
old) and old
    adults (24 to 28 months old). In addition, some rats had brain
lesions that had
    destroyed some of the neurons in the cholinergic system. Other rats
had no lesions.

    The researchers found that, at baseline, both older and younger rats
with lesions
    showed a similar decline in the release of ACh in the cereberal
cortex of the brain.

    However, when the rats were presented with a stimulus -- the
appearance of darkness
    and food -- the older rats with lesions reacted very differently
when compared with
    young animals with similar lesions.

    The young rats with lesions still showed a significant increase in
ACh release of 60 to
    120 percent (compared to baseline) when presented with darkness and
    However, the older lesioned rats showed a very weak and
insignificant response --
    only a 20 to 40 percent increase in ACh release.

    The rats with normal brains (no lesions) did not show such a
significant difference
    between young and old rats. The young non-lesioned rats showed an
increased ACh
    release of about 100 to 180 percent when presented with darkness and
food, similar
    to that found in older non-lesioned rats.

    Sarter said it was significant that young rats, even when they lost
part of their
    cholinergic sytems due to lesions, were still able to respond
robustly to the stimulus
    of darkness and food. It was only the older rats with lesions who
did not respond to
    the darkness and food stimulus. If something similar happens in
humans, it suggests
    that people with some kinds of pre-existing brain pathologies may
not realize it until
    the aging process starts and it triggers Alzheimer's or other forms
of dementia.

    "This is something new for us -- to see an interaction between the
aging process and a
    compromised brain," Sarter said. "We believe that people who develop
    disease have something wrong with their brain long before the
symptoms appear. It is
    the aging process that then makes the disease appear."

    Sarter said it is not yet known exactly what pathologies some people
may have in their
    brains that lead them to develop Alzheimer's disease as they age.
Most likely, there is
    some kind of damage to the neurons in the cholinergic system, he
said. Sarter said it is
    also not known what happens during aging that interacts with
pre-existing conditions
    to cause dementia. "Aging research is really just beginning and we
have a lot to
    learn," he said.

    However, these findings suggest that if scientists can find how to
identify people with
    brain pathologies that will lead to Alzheimer's, new treatments
could be developed
    that will prevent or at least reduce the symptoms of the disease.

    "Maybe if we start early enough, we can keep the neurons alive and
working into old
    age," Sarter said.


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