X-Message-Number: 5655
From: Peter Merel <>
Subject: SCI.CRYONICS Enteric Nervous System and neurosuspension.
Date: Tue, 23 Jan 1996 20:24:25 +1100 (EST)

The following is excerpted without permission from 

http://www2.nando.net/newsroom/ntn/health/012296/health24_25186.html

> Copyright ) 1996 Nando.net
> Copyright ) 1996 N.Y. Times News Service
> 
>[...]
> The gut's brain, known as the enteric nervous system, is located in
> sheaths of tissue lining the esophagus, stomach, small intestine and
> colon. Considered a single entity, it is packed with neurons,
> neurotransmitters and proteins that zap messages between neurons,
> support cells like those found in the brain proper and a complex
> circuitry that enables it to act independently, learn, remember and,
> as the saying goes, produce gut feelings.
> 
> The brain in the gut plays a major role in human happiness and misery.
> But few people know it exists, said Dr. Michael Gershon, a professor
> of anatomy and cell biology at Columbia-Presbyterian Medical Center in
> New York. For years, people who had ulcers, problems swallowing or
> chronic abdominal pain were told that their problems were imaginary,
> emotional, simply all in their heads, Gershon said. They were shuttled
> to psychiatrists for treatment.
> 
[...]
> Details of how the enteric nervous system mirrors the central nervous
> system have been emerging in recent years, said Gershon, who is
> considered one of the founders of a new field of medicine called
> neurogastroenterology.
> 
> Nearly every substance that helps run and control the brain has turned
> up in the gut, Gershon said. Major neurotransmitters like serotonin,
> dopamine, glutamate, norepinephrine and nitric oxide are there. Two
> dozen small brain proteins, called neuropeptides, are in the gut, as
> are major cells of the immune system. Enkephalins, one class of the
> body's natural opiates, are in the gut. And in a finding that stumps
> researchers, the gut is a rich source of benzodiazepines -- the family
> of psychoactive chemicals that includes such ever popular drugs as
> Valium and Xanax.
> 
[...]
> This is indeed the picture seen by developmental biologists. A clump
> of tissue called the neural crest forms early in embryogenesis,
> Gershon said. One section turns into the central nervous system.
> Another piece migrates to become the enteric nervous system. Only
> later are the two nervous systems connected via a cable called the
> vagus nerve.
> 
[...]
> Trouble is, no one bothered to count the nerve fibers in the gut. When
> they did, he said, they were surprised to find that the gut contains
> 100 million neurons -- more than the spinal cord has. Yet the vagus
> nerve only sends a couple of thousand nerve fibers to the gut.
> 
> The brain sends signals to the gut by talking to a small number of
> "command neurons," which in turn send signals to gut interneurons that
> carry messages up and down the pike, Gershon said. Both command
> neurons and interneurons are spread throughout two layers of gut
> tissue called the myenteric plexus and the submuscosal plexus. ("Solar
> plexus" is actually a boxing term that refers simply to nerves in the
> abdomen.)
> 
> Command neurons control the pattern of activity in the gut, Gershon
> said. The vagus nerve only turns the volume by changing its rates of
> firing.
> 
> The plexuses also contain glial cells that nourish neurons, mast cells
> involved in immune responses, and a "blood brain barrier" that keeps
> harmful substances away from important neurons, Gershon said. They
> have sensors for sugar, protein, acidity and other chemical factors
> that might monitor the progress of digestion, determining how the gut
> mixes and propels its contents. "It's not a simple pathway," he said.
> "It uses complex integrated circuits not unlike those found in the
> brain."
> 
> The gut's brain and the head's brain act the same way when they are
> deprived of input from the outside world, Wingate said. During sleep,
> the head's brain produces 90-minute cycles of slow wave sleep
> punctuated by periods of rapid eye movement sleep in which dreams
> occur. During the night, when it has no food, the gut's brain produces
> 90-minute cycles of slow wave muscle contractions punctuated by short
> bursts of rapid muscle movements, Wingate said.
> 
[...]
> Such cross talk also explains many drug interactions, Gershon said.
> "When you make a drug to have psychic effects on the brain, it's very
> likely to have an effect on the gut that you didn't think about," he
> said. Conversely, drugs developed for the brain could have uses in the
> gut.
> 
[...]
> Some antibiotics like erythromycin act on gut receptors to produce
> oscillations, Gershon said. People experience cramps and nausea. Drugs
> like morphine and heroin attach to the gut's opiate receptors,
> producing constipation. Indeed, both brains can be addicted to
> opiates.
> 
> Victims of Alzheimer's and Parkinson's diseases suffer from
> constipation. The nerves in their gut are as sick as the nerve cells
> in their brains.
> 
> Just as the the central brain affects the gut, the gut's brain can
> talk back to the head, Gershon said. Most of the gut sensations that
> enter conscious awareness are negative things like pain and
> bloatedness, Wingate said. We don't expect to feel anything good from
> the gut, but that doesn't mean such signals are absent, he said.
> 
> Hence, the intriguing question: Why does the human gut produce
> benzodiazepine? The human brain contains receptors for benzodiazepine,
> a drug that relieves anxiety, suggesting that the body produces its
> own internal source of the drug, said Dr. Anthony Basile, a
> neurochemist in the Neuroscience Laboratory at the National Institutes
> of Health in Bethesda, Md.
> 
[...]
> The human gut has long been seen as a repository of good and bad
> feelings. Perhaps emotional states from the head's brain are mirrored
> in the gut's brain, where they are felt by those who pay attention to
> them.

Perhaps this is a good reason not to go neuro? Or should neuro cases
preserve their enteric nervous systems as well as spinal cords and brains?

Peter Merel.


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