AJP - Gastrointestinal and Liver Physiology, Vol 264, Issue 4 655-G658, Copyright © 1993 by American Physiological Society
Kainic acid injection into medullary raphe produces gastric lesions through the vagal system in rats
T. Okumura, A. Uehara, Y. Taniguchi, Y. Watanabe, K. Tsuji, S. Kitamori and M. Namiki
Department of Internal Medicine (III), Asahikawa Medical College, Hokkaido, Japan.
There is little evidence of a role of nuclei in the brain stem, other than
the dorsal motor nucleus of the vagus nerve in the medulla oblongata, in
terms of central mechanisms for gastric ulcer formation. Recent reports
suggest that the medullary raphe nuclei may be involved in the central
regulation of gastric functions such as gastric acid secretion and
motility. In the present study, we examined whether neurons in the nucleus
raphe obscurus (NRO) played a significant role in the formation of gastric
ulcers with the use of Sprague-Dawley rats. First, we determined whether
excitation of the medullary raphe resulted in the development of gastric
lesions. Chemical stimulation of neurons in the NRO by kainic acid produced
gastric erosions within 4 h in 24-h fasted rats. Saline tested under the
same conditions did not modify the integrity of the gastric mucosa. It was
also demonstrated that kainic acid injection outside the raphe obscurus
boundaries failed to develop gastric lesions. Next, we examined the effects
of the vagal system on the gastric lesion formation induced by stimulation
of the raphe nucleus. Bilateral gastric branch vagotomies completely
prevented the development of the raphe nucleus-provoked gastric mucosal
damage. All these results suggest, for the first time, that excitation of
neurons in the medullary raphe obscurus induces gastric ulceration through
vagal stimulation.
