You know how people are always telling you your brains are in your
behind? Well, they could be right. Check out this instalment of
mystery neuroscientist's newsletter.
(I wasn't going to make a habit of these posts. But I found this so
interesting yet off-the-wall I had to share it.)
-Stephen
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Date: Fri, 31 Mar 2000 05:27:37 -0800
From: Mystery neuroscientist
Subject: BioPsych/ Neurogastroenterology
U.S. News & World Report
Science & Ideas 4/3/00
The wisdom of the gut Those butterflies in your stomach are not just in your mind
By Rachel K. Sobel
For reasons that still mystify researchers today, the stunning results
of this experiment went into hibernation for nearly half a century and
are only now receiving fresh validation. Indeed, no one in medicine
paid attention again until a fledgling neurobiologist began touting
its clinical value in 1965. "The idea that the gut can be operating
its own nervous system was shocking," recalls Michael Gershon, now
chair of the department of anatomy and cell biology at Columbia
University and author of The Second Brain, a 1998 account of the
acceptance of this scientific idea. Since the 1980s, Gershon's
colleagues have zealously embraced the notion of "the little brain in
the gut," as it's affectionately known. "What Mother Nature had done,
rather than packing all of those neurons in the big brain in the skull
and sending long lines to the gut, is distribute the microcomputer,
the little brain, right along with the gut," says Jackie Wood, a
neurobiologist at Ohio State University.
Now a full-blown renaissance in neurogastroenterology, the
nine-syllable code word for the study of the nerves entrenched in the
lining of the esophagus, stomach, small intestine, and colon has
researchers probing the depths of the digestive nervous system with
feverish intensity and surfacing with remarkable insights. This new
breed of neuroscientist, 300 strong, and counting, is shaping a novel
notion of the gut and deriving innovative ways to treat its ailments.
Last month, for example, the first drug ever designed for
irritable-bowel syndrome (IBS), called Lotronex, arrived in doctors'
offices. It's based on this new understanding of the sentient gut and
may, in fact, change the way physicians handle this and related
disorders.
Daily chores. By peeling away the layers of padding that surround the
digestive tract, scientists have indeed unearthed some of the buried
secrets of the little brain. This miniature central processing unit,
whose 100 million-plus nerves number more than those in the spinal
cord, carries out many of its daily chores without guidance from the
brain. "Suppose the gut gets a message that the pressure is up in the
stomach. The brain doesn't get its hands dirty with that kind of
nonsense so the gut takes care of it," explains Gershon. Not only does
the gut direct its own show, he adds, but its spidery projections
trickle into neighboring organs, commanding the pancreas and
gallbladder to aid with digestion.
Though able to run itself, the little brain does stay in close touch
with the big brain via 1,000 or so nerve fibers. Scientists studying
this relationship have discovered that the gut-brain connection is at
the heart of some of the most visceral human emotions. A "gut
feeling," for example, isn't just a poetic conceit used to convey
intuition. It arises from the biological interplay between these two
intimately connected brains, says Emeran Mayer, a gastroenterologist
and professor of physiology at the University of California-Los
Angeles. When faced with an anxiety-ridden situation, the big brain
sends urgent messages to the little brain, which begins orchestrating
a physical response, read as gurgling or "butterflies" in the stomach.
These sensations are recorded in an "emotional memory bank" residing
in the big brain, says Mayer, and the next time the big brain makes a
decision in a similar situation, it's not based on some intellectual
calculation. Rather, it's instantaneously formulated from this catalog
of previous bodily responses, gut feelings", stored in the brain.
Why some people feel the burden of stress in their gu and not for
instance, in their heart can also be explained by the close
communication between the brain and the gut. When the big brain
consciously perceives a stressful situation, it calls on its fraternal
twin through specialized cells called mast cells embedded in the gut's
lining. These mast cells secrete a chemical called histamine, which
activates the nerves controlling the gut, telling the muscles to
contract. Hence, the cramps and bathroom trips so often associated
with bouts of stress.
The complex circuitry in the gut not only operates like a brain; it
looks uncannily similar to one, too. Just like the nerves in the brain
and spinal cord, those in the gut are naked, lacking an insulating
sheath that wraps around the rest of the body's nerves. Swishing among
the gut's nerves are serotonin, nitric oxide, carbon monoxide, and at
least 30 other neurochemicals, the same ones sloshing around in the
skull. Curiously enough, as healthy brains in the head and gut
resemble each other, so too do diseased ones. Scientists have found
that some Alzheimer's and Parkinson's patients accumulate the same
type of tissue damage in their bowels as they do in their skulls,
raising the possibility that these disorders might someday be
diagnosed by routine rectal biopsy.
The fact that the two brains share so much of the same
biology can explain why psychiatric medications have side effects in
the gut. Antidepressants like Prozac, for instance, increase the
presence of serotonin in the spaces where nerves talk to each other in
both brains. While this neurochemical shift settles the big brain
emotionally, it causes the gut to squirm, leading to side effects like
abdominal cramping and diarrhea.
Many investigators are taking their cues in treating gut disorders
from drugs that have worked on the brain. For example, Michael
Camilleri, a gastroenterologist at the Mayo Clinic, is treating a
variety of gastrointestinal disorders with Clonidine, a drug sometimes
used in psychiatry. Another medication called Imitrex, customarily
used to soothe the pangs of migraine headaches, has effectively healed
the gut in two studies by Belgian teams. And Lotronex, the recently
released treatment for irritable-bowel syndrome, came from an
anti-anxiety drug.
If the arrival of Lotronex signals a new era in treatment, it also
goes a long way in debunking the popular notion that IBS is "all in
the head." Though IBS is a relatively common disorder, affecting as
many as 1 in 5 people, it is difficult to diagnose with conventional
methods. The chronic abdominal pain, discomfort, and irregular bowel
movements leave no trace in the lining of the gut because such
abnormalities presumably occur at the level of the nerves tucked
inside the gut. This lack of physiological evidence has led many
doctors to dismiss patients' complaints as psychosomatic. It's now
hypothesized that the nerves lining the gut are oversensitive and
overreact to gas and food passing by, thus causing pain and cramping.
"Lotronex suggests that there is a mechanism that is malfunctioning
either in the big brain or the little brain, or both, or someplace in
between," says Wood. "IBS is not imagined."
U.S.News & World Report Inc. All rights reserved.
http://www.usnews.com/usnews/issue/000403/gut.htm
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Stephen Black, Ph.D. tel: (819) 822-9600 ext 2470
Department of Psychology fax: (819) 822-9661
Bishop's University e-mail: [EMAIL PROTECTED]
Lennoxville, QC
J1M 1Z7
Canada Department web page at http://www.ubishops.ca/ccc/div/soc/psy
Check out TIPS listserv for teachers of psychology at:
http://www.frostburg.edu/dept/psyc/southerly/tips/
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