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Learning & Memory Research

Ian Goddard igoddard at erols.mom
Fri Mar 15 10:22:14 EST 2002


University of Houston - N E W S   R E L E A S E 

 UH Researchers Find Learning Associated With
   Increase in Transport Molecules in Brain

HOUSTON, March 12, 2002 - Can't remember where
you put your keys, or how to retrieve your
voicemail? Your brain's cleaning crew may be
asleep on the job.

Molecular "brooms" that whisk away excess
amounts of the chemical glutamate in the brain
may play a key role in learning and memory
formation, suggest recent animal studies by
scientists at the University of Houston.

In the brain, several chemicals called
neurotransmitters carry messages in the spaces
connecting one nerve cell, or neuron, to the
next, allowing the brain to function properly.
Scientists believe that the strengthening of
these connections by the neurotransmitter
glutamate - a process called long-term
potentiation - is one mechanism responsible
for the storage of some memories.
Now, for the first time, researchers at the
University of Houston have determined that
levels of transport molecules for glutamate -
chemicals that latch on to and "sweep away"
glutamate - increase during learning,
suggesting that this molecular cleaning crew
has an important role in the process.

In experiments with rats, the UH team found
that glutamate transport molecules increased
by more than 100 percent in a region of the
brain called the hippocampus 30 minutes after
the onset of long-term potentiation - the
memory-forming process.

"These results suggest that the regulation of
glutamate uptake by the transport molecules
may be important for maintaining the strength
of connections among the neurons in the area
of the brain associated with memory," says UH
biochemist Arnold Eskin, one of the authors of
a study appearing in the February issue of
Nature Neuroscience.

"We imagine that the way the nervous system
stores information in rats is similar to the
way it might work in humans," he says. "Maybe
there are people who can't learn as well
because their transporters are out of whack,
or have memory problems because there are
deficiencies in their glutamate transporters.
Before we did these studies no one was even
asking these questions. Now we have a
fundamental reason to investigate this
mechanism further.

"We knew that glutamate is involved in
learning, but our study is the first to
investigate the role of glutamate transporters
and glutamate uptake in the learning and
memory formation process," Eskin says.

In the rat studies, which have been
successfully reproduced, Eskin and his
research team first trained the animals
repeatedly over a period of time, which
produced a change in behavior in the rats.
They then examined the transporters in the
animals' hippocampus region.

"The way you know that the animal remembers
what you've done is because its behavior has
changed as a result of experience, which is
the definition of learning," Eskin says. "Its
nervous system remembers that event, and we
know there have been changes in the system
because the animal gives us a different

UH doctoral student Jonanthan Levenson
performed most of the research, assisted by 
UH undergraduate student Lorna Kategaya and
Baylor College of Medicine researchers Edwin
Weeber, Joel Selcher and J. David Sweatt. 
All are co-authors on the study. Eskin says 
the job of glutamate transporters in the 
brain is two-fold.

"Clearing away neurotransmitters allows the
next batch of chemical messengers to deliver 
a 'clean' signal between neurons," he says.
"Also, in the case of glutamate, which
desensitizes its receptors and kills nerve
cells if too much hangs around too long,
transport molecules are essential to
maintaining effective transmission and a
non-toxic environment in the brain."

Other studies have suggested that deficiencies
in glutamate transporters may be responsible
for neuron damage and death associated with
neurodegenerative diseases such as amyotrophic
lateral sclerosis, or Lou Gherig's disease.

Eskin's research is funded by the National
Institutes of Health.

About the University of Houston

The University of Houston, Texas' premier
metropolitan research and teaching
institution, is home to more than 40 research
centers and institutes and sponsors more than
300 partnerships with corporate, civic and
governmental entities. UH, the most diverse
research university in the country, stands at
the forefront of education, research and
service with more than 32,000 students.


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