The central pattern generator for vomiting may exist in the reticular area dorsomedial to the retrofacial nucleus in dogs |
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Authors: | T Koga R Qu Hiroyuki Fukuda |
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Institution: | (1) Department of Physiology, Kawasaki Medical School, Kurashiki, Okayama 701-01, Japan Tel.: +81-86-462-1111, Fax: +81-86-462-1199, e-mail: koga@med.kawasaki-m.ac.jp, JP |
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Abstract: | There is some controversy over whether or not a discrete site that integrates vomiting activities in somatic and autonomic
nerves is present in the medulla oblongata. On the basis of our previous studies, we hypothesized that the temporal patterns
of muscle contractions in vomiting are generated by a central pattern generator in the retrofacial area of the rostral medulla.
To investigate this hypothesis further, the effects of electrical and chemical lesions of the medullary area were observed
in decerebrate paralyzed dogs. Efferent activities of the phrenic and abdominal muscle nerves were recorded to recognize fictive
vomiting. The right half of the medulla oblongata was transversely severed about 3 mm rostral to the obex. Fictive vomiting
responses to vagal stimulation still appeared after hemisection in all 11 dogs. In addition, stimulation of the contralateral
reticular area dorsomedial to the retrofacial nucleus produced fictive vomiting even after hemisection. An electrical lesion
or injection of kainic acid (0.5–1.0 μl) was applied at the point where reticular stimulation induced fictive vomiting. After
this destruction, no activities that corresponded to fictive vomiting could be induced by stimulation of vagal afferents or
the reticular site. Salivation was decreased by hemisection, and decreased further, but was not completely abolished, with
destruction of the reticular area. Kainic acid is known to selectively destroy neural cell bodies. Therefore, we concluded
that neuronal somata in the reticular formation dorsomedial to the retrofacial nucleus play an essential role in the central
patterning of vomiting activities in peripheral motor nerves.
Received: 10 September 1996 / Accepted: 2 July 1997 |
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Keywords: | Vomiting Retrofacial nucleus Kainic acid |
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