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A gastrointestinal role for the amphibian ‘diaphragm’ of Xenopus laevis
Published online by Cambridge University Press: 12 August 2004
Abstract
The ‘diaphragm’ of Xenopus laevis has close anatomical relations to the lower end of the oesophagus. In mammals, the crural diaphragm acts as a pinch valve at the gastro-oesophageal junction and is an important component of the gastro-oesophageal reflux barrier. The present study analysed the effect of amphibian ‘diaphragm’ contraction on oesophageal pressure using a superfused in situ oesophago-diaphragmatic preparation of large female Xenopus. Three-dimensional reconstruction of the oesophageal pressure profile was performed using four-port oesophageal infusion manometry. Bilateral electrical stimulation of the nerves supplying the ‘diaphragm’ of Xenopus increased the pressure volume vector of 5 mm of oesophagus (centred around the insertions of the diaphragm) from 20.4±16 to 553.6±232 mm.mmHg2 (mean±sd). This was a statistically significant increase and statistically significantly higher than that evoked by electrical stimulation of both vagi (28.1±30.7 mm.mmHg2). The amphibian ‘diaphragm’ seems to be functionally similar to the mammalian crural diaphragm. By analogy, we suggest that the original role of the diaphragm was not respiratory but gastrointestinal.
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- © 2004 The Zoological Society of London
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