Received: by alpheratz.cpm.aca.mmu.ac.uk id BAA02480 (8.6.9/5.3[ref pg@gmsl.co.uk] for cpm.aca.mmu.ac.uk from fmb-majordomo@mmu.ac.uk); Fri, 21 Dec 2001 01:40:55 GMT Message-Id: <200112210136.fBL1aF115444@sherri.harvard.edu> Subject: Re: Fwd: Eureka! Date: Thu, 20 Dec 2001 20:36:19 -0500 x-sender: wsmith1@camail.harvard.edu x-mailer: Claris Emailer 2.0v3, Claritas Est Veritas From: "Wade T. Smith" <wade_smith@harvard.edu> To: "Memetics Discussion List" <memetics@mmu.ac.uk> Content-Type: text/plain; charset="US-ASCII" Sender: fmb-majordomo@mmu.ac.uk Precedence: bulk Reply-To: memetics@mmu.ac.uk
Hi Philip Jonkers -
>Also it makes sense for the brain to reward events of
>relief of confusion as it so reinforces/encourages
>attempts to resolve future events of confusion.
From SciAm online-
- Wade
*********
Beating Abuse
-By Tabitha M. Powledge
Glutamate May Hold a Key to Drug Addiction
http://www.sciam.com/2002/0102issue/0102scicit5.html
Addiction has long been thought to be a form of learning. In the past few
years, molecular biologists have amassed chemical evidence to prove it,
in the process generating new ideas for combating drug use.
Some of the most striking recent studies have examined the affinity
between cocaine and glutamate, one of several chemical neurotransmitters
that govern communication between nerve cells and are involved
particularly with memory. For example, Stanislav R. Vorel and his
colleagues at the Albert Einstein College of Medicine discovered that
electrically stimulating the hippocampus, a brain structure central to
memory and rich in glutamate, causes dependence relapse in rats formerly
addicted to cocaine. Other researchers found that glutamate activates
brain cells devoted to dopamine, a neurotransmitter associated with
feelings of reward and pleasure. Indeed, the dopamine reward circuit in
the brain has been regarded as the addiction pathway, commandeered not
just by cocaine but by all addictive drugs. The fact that glutamate
modifies dopamine action demonstrates a direct connection between brain
reward circuits and those for learning and memory.
The reward and memory systems may harbor the secrets to addiction, but
they also serve as a barrier to developing treatments. Altering either of
these fundamental brain circuits without subverting some essential
function is tricky business. "That's why there was excitement about the
possibility that the glutamate system might be involved. But at this
point, we're not there," says Francis J. White, a pharmacologist at Finch
University of Health Sciences/The Chicago Medical School.
A discovery published in September 2001 may nudge that process along.
Researchers studying mice identified a particular glutamate receptor,
known as mGluR5, that is crucial for cocaine dependence. Mice that lack
the receptor do not become dependent no matter how much cocaine they are
given. The mGluR5 findings are significant in part because the receptor's
action appears to be selective. The mutant mouse takes food and water
just like other mice, which suggests that lack of the receptor does not
affect "natural" rewards, only interest in cocaine.
Eliot Gardner, a senior research investigator at the National Institute
on Drug Abuse, identifies two major hurdles to basing addiction
treatments on glutamate. The first is figuring out which glutamate
receptors are involved. (Even if mGluR5 is related to human cocaine
dependence, it is not the only receptor significant in addiction.) The
second problem is glutamate's ubiquity. "It's found all over the brain in
lots of circuits subserving lots of behavior and mental processes that
one would not want to manipulate," Gardner says. Researchers will need to
find precise delivery systems that will target only specific brain
circuits, leaving alone the dozens, or perhaps hundreds, of other
circuits that use glutamate as a neurotransmitter.
Intriguingly, the glutamate studies could strengthen that old
nonpharmaceutical standby: behavioral therapy. One of the most promising
treatments "is to have people unlearn aspects of addiction and relearn
new things to do in life," says renowned molecular biologist and
addiction specialist Eric J. Nestler of the University of Texas
Southwestern Medical Center. "An argument can be made that Alcoholics
Anonymous provides that type of alternative focus." Or pharmacotherapies
could be combined with "talking cures" to yield fewer relapses. "If we
could develop medications that could address the underlying biology, the
powerful biological forces that drive addiction, then we can make a
person more amenable to other treatments," such as behavior therapy,
Nestler says. "You really need both."
DRUGS FOR DRUG ABUSE
The hunt for addiction treatments grows more intense every year. The
National Institute on Drug Abuse is conducting clinical tests on more
than 60 compounds for cocaine and opiate dependence alone and also a few
for methamphetamine, according to Francis Vocci, who directs NIDA's
Division of Treatment Research and Development. In addition to some
compounds that act on glutamate and dopamine, researchers are looking at
other targets. Chemicals that block the action of stress hormones are
effective against opiates, cocaine, amphetamines and alcohol, Vocci
reports, which means that a magic bullet that works against mechanisms
underlying all addictive drugs is not utterly out of the question.
===============================================================
This was distributed via the memetics list associated with the
Journal of Memetics - Evolutionary Models of Information Transmission
For information about the journal and the list (e.g. unsubscribing)
see: http://www.cpm.mmu.ac.uk/jom-emit
This archive was generated by hypermail 2b29 : Fri Dec 21 2001 - 01:47:22 GMT