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An arterially perfused decerebrate preparation of Suncus murinus (house musk shrew) for the study of emesis and swallowing

Published online by Cambridge University Press:  21 August 2002

Julia E. Smith
Affiliation:
Department of Physiology, St George's Hospital Medical School, London SW17 0RE and Department of Physiology, School of Medical Sciences, University of Bristol, Bristol BS81TD, UK
Julian F. R. Paton
Affiliation:
Department of Physiology, St George's Hospital Medical School, London SW17 0RE and Department of Physiology, School of Medical Sciences, University of Bristol, Bristol BS81TD, UK
Paul L. R. Andrews
Affiliation:
Department of Physiology, St George's Hospital Medical School, London SW17 0RE and Department of Physiology, School of Medical Sciences, University of Bristol, Bristol BS81TD, UK
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Abstract

Arterially perfused, decerebrate preparations of the insectivore, Suncus murinus were made to determine whether the emetic reflex could be activated in such a preparation using a range of stimuli shown to be emetic in conscious or anaesthetised Suncus. Efferent phrenic and vagus nerve activities and electromyograms (EMGs) from the temporalis, abdominal oesophagus and trapezius muscles were recorded, as well as longitudinal shortening of the oesophagus and dorso-ventral movements of the thorax. The preparations swallowed spontaneously every 0.6 to 6.5 min. The duration of a swallow was 3.1 ± 0.3 s (recorded as the time taken for the oesophagus to shorten and recover to its resting position) and the oesophagus shortened by 3.5 ± 0.4 mm during a swallow. The emetic reflex was activated by electrical stimulation (30 Hz, 10-20 V, 0.2 ms pulse width, for 30 s) of abdominal vagal afferents (latency < 30 s) or by arterial perfusion with either 40 nM of the capsaicin analogue resiniferatoxin (latency 1.7 ± 0.6 min), 6 µM nicotine (latency 1.6 ± 0.1 min) or 1 µM of the phosphodiesterase IV inhibitor CP-80,633 (latency 8.9 ± 3.9 min). These emetic stimuli produced somatic and visceral movements in Suncus preparations indicative of activation of the emetic reflex. There were pronounced contractions of the thorax that occurred simultaneously with oesophageal shortening and mouth opening, separated by thorax expansion and a burst of phrenic nerve activity. During emetic-like episodes, oesophageal shortenings were only 0.84 ± 0.1 s in duration, faster than the duration of shortening observed during swallowing (cf. swallowing, 3.1 ± 0.3 s; P < 0.0001). The shortening of the oesophagus during emetic-like episodes was 6.2 ± 0.4 mm, which was greater than the shortening seen during swallowing (cf. swallowing, 3.5 ± 0.4 mm; P < 0.0001). We conclude that the emetic reflex can be activated in our Suncus preparations and that this non-sentient small adult animal model can now be used to study the neurophysiology and pharmacology of swallowing and emesis. Experimental Physiology (2002) 87.5, 563-574.

Type
Full Length Papers
Copyright
© The Physiological Society 2002

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