Subject: Neuroinflammation in the second brain

      Neurogastroenterol Motil. 2005 Feb;17(1):4-15.  

Plasticity of the enteric nervous system during intestinal inflammation.

Lomax AE, Fernandez E, Sharkey KA.

Department of Physiology and Biophysics, Gastrointestinal, Neuroscience and Mucosal Inflammation Research Groups, University of Calgary, Calgary, Alberta, Canada.

Inflammation of the bowel causes structural and functional changes to the enteric nervous system (ENS). While morphological alterations to the ENS are evident in some inflammatory conditions, it appears that relatively subtle modifications to the neurophysiology of enteric microcircuits may play a role in gastrointestinal (GI) dysfunction. These include changes to the excitability and synaptic properties of enteric neurones. The response of the ENS to inflammation varies according to the site and type of inflammation, with the functional consequences depending on the nature of the inflammatory stimulus. It has become clear that inflammation at one site can produce changes that occur at remotes sites in the GI tract. Immunohistochemical data from patients with inflammatory bowel disease (IBD) and animal models indicate that inflammation alters the neurochemical content of some functional classes of enteric neurones. A growing body of evidence supports an active role for enteric glia in neuronal and neuroimmune communication in the GI tract, particularly during inflammation. In conclusion, plasticity of the ENS is a feature of intestinal inflammation. Elucidation of the mechanisms whereby inflammation alters enteric neural control of GI functions may lead to novel treatments for IBD.

Learning and Memory Stimulated By Gut Hormone

http://www.eurekalert.org/pub_releases/2006-02/yu-lam022206.php

Researchers at Yale School of Medicine have found evidence that a hormone produced in the stomach directly stimulates the higher brain functions of spatial learning and memory development, and further suggests that we may learn best on an empty stomach.

Published in the February 19 online issue of Nature Neuroscience by investigators at Yale and other institutes, the study showed that the hormone ghrelin, produced in the stomach and previously associated with growth hormone release and appetite, has a direct, rapid and powerful influence on the hippocampus, a higher brain region critical for learning and memory. The team, led by Tamas L. Horvath, chair and associate professor of the Section of Comparative Medicine at Yale School of Medicine, and associate professor in the Department of Obstetrics, Gynecology & Reproductive Sciences, and Neurobiology, first observed that peripheral ghrelin can enter the hippocampus and bind to local neurons promoting alterations in connections between nerve cells in mice and rats. Further study of behavior in the animals showed that these changes in brain circuitry are linked to enhanced learning and memory performance. Because ghrelin is highest in the circulation during the day and when the stomach is empty, these results also indicate that learning may be most effective before meal-time. "Based on our observations in animal models, a practical recommendation could be that children may benefit from not overeating at breakfast in order to make the most out of their morning hours at school,"said Horvath. "The current obesity epidemic among American school children, which to some degree has been attributed to bad eating habits in the school environment, has been paralleled by a decline of learning performance. It is however too early to speculate if hormonal links between eating and learning are involved in that phenomenon."

Horvath said that high ghrelin levels or administration of ghrelin-like drugs could also protect against certain forms of dementia, because aging and obesity are associated with a decline in ghrelin levels and an increased incidence of conditions of memory loss like Alzheimer's disease.

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