Effects of Vagal Deafferentation on Oesophageal Motility in the Conscious Sheep

Abstract

The pharyngeal and oesophageal stages of swallowing depend on a central pattern generator. This theory has come from the early observation of MOSSO (1876) that primary peristalsis could jump a gap produced by oesophageal transection in dog. More recent studies of the effects of oesophageal transection (CARVETH, SCHLEGEL, CODE and ELLIS, 1962) and demonstration that sequential efferent signals proceed to all oesophageal muscles (ROMAN, 1966; ROMAN and TIEFFENBACH, 1972) support this theory that mammalian nervous control of peristalsis is governed by a central pattern generator. However, the decrease in the number of peristaltic waves observed following deviation of the bolus (JANSSENS, 1978) suggests that control of oesophageal peristalsis depends on peripheral feedback. Direct evidence for oesophageal afferents has come from neural recordings. The passage of a peristaltic wave and distension of the oesophagus elicited discharges in sensory fibres (ANDREW, 1946; MEI, 1970; FALEMPIN, MEI and ROUSSEAU, 1978; FALEMPIN and ROUSSEAU, 1983). In spite of the evidence that swallowing depends on a central pattern generator, peripheral inputs to the medullary centres seem to modify the central neural program. So the contribution of afferents in the control of the swallowing centre could be evaluated if the contingent of sensory fibres alone was cut in both vagus nerves. The surgical isolation of the vagal sensory fibres is actually possible at the level of the nodose ganglion in sheep. However as cutting both ganglia, leaving the bundles of motor fibres intact, is followed by death of the sheep in most cases, section of one vagus nerve was associated in the present work with division of the nodose ganglion of the contralateral nerve to test the effects of vagal deafferentation on electromyographic oesophageal activity and transit of a bolus.