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. Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=5655