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Recent Advances in Physiology of Defecation Sosogu Nakayama 1 1Dept. of Physiology, Okayama University Medical School pp.1257-1266
Published Date 1971/9/25
DOI https://doi.org/10.11477/mf.1403111568
  • Abstract
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 1. Even in the rectum isolated from the central nervous system, the defecation occurs. Mucosal stimulation of the colon or rectum excites the motility above and inhibits it below the spot stimulated.

Because the responses disappear completely after intravenous administration of CE or tetrodotoxin, it is supposed that the receptors are located in the mucosa and the reflex center in the Auerbach's plexus. Such a view is substantiated by the experimental results of perfusion of the colon and the insertion of the bolus into the colonic lumen: The perfusion of the colonic lumen with the pressure of 12 cm H2O of over causes the mass peristalsis, resulting in the outflow of fluid (Nanba, 1960). The insertion of the bolus into the colonic lumen produces anally inhibition of the colonic motility and orally the mass peristalsis (Nakayanla, 1963). It is considered that such a mechanism plays a role on the colonic and rectal movements to cause defecation.

 2. Distension of the denervated rectum causes relaxation of the internal anal sphincter. It is therefore concluded that the stretch receptors are located in the mucosa or the muscular layer, and that the responses are elicited by a mechanism similar to that mentioned above.

 3. Adrenergic agents sometimes cause contraction and sometimes relaxation of the internal anal sphincter. It is suggested that the internal sphincter muscle contains α-adrenergic receptors subserving contraction, and fi-receptors subserving relaxation, and that it is generally insensitive or less sensitive to acetylcholine.

 4. Many investigators have reported that electric stimulation of the amygdaloid nuclei and periarnygclaloid cortex causes defecation and micturition. Watanabe in the author's laboratory has demonstrated that electric stimulation of the amygdaloicl nuclei or peria mygdaloid cortex produces the contraction or relaxation of the colon, rectum and internal anal sphincter in dogs.

 5. Judging from the questionaires about defecation among the medical students, the author presumes a possibility that the limbic system participates in the morning defecation, and also gives his opinion on the question whether or not the higher defecation center is located in the medulla oblongata.


Copyright © 1971, Igaku-Shoin Ltd. All rights reserved.

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電子版ISSN 1882-1219 印刷版ISSN 0536-2180 医学書院

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