A MULTIDISCIPLINARY STUDY INTO CHANGES IN THE VAGUS NERVE FOLLOWING PARTIAL CHRONIC VAGOTOMY

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dc.contributor.authorASALA, SAMUEL ABAYOMI
dc.date.accessioned2014-02-05T10:51:01Z
dc.date.available2014-02-05T10:51:01Z
dc.date.issued1984-02
dc.descriptionA thesis submitted for the degree of Doctor of Philosophy in the University of Sheffield, U.K. DEPARTMENT OF ANATOMY AND CELL BIOLOGYen_US
dc.description.abstractThe ferret was used as a model for studying the effect of chronic abdominal partial vagotomy on gastric motility and innervation of the gastric wall by the surviving abdominal vagal trunk. The fibre composition of the vagus nerve trunks was also determined and correlated as much as possible with the results of the two series of experiments above. Gastric motility was measured indirectly by measuring the intragastric pressure that was associated with it in response to stimulation of the cervical vagus nerves. Acute ventral trunk vagotomy did not significantly reduce the intragastric pressure response to cervical vagal stimulation. Similarly, following chronic ventral trunk vagotomy, intragastric pressure response to cervical vagal stimulation did not differ significantly from the acute and control values until after three months when it increased significantly above acute values probably as a result of re-innervation of the gastric wall by regenerative sprouts from the proximal nerve segment. Acute dorsal trunk vagotomy resulted in a significant reduction of intragastric pressure response to cervical vagal stimulation below control values. Following chronic dorsal trunk vagotomy, intragastric pressure response to cervical vagal stimulation significantly increased above the acute value and reached the control value five days after vagotomy. The intragastric pressure maintained a plateau at this normal value throughout the three months period of the experiments. Regenerative sprouts were not seen after chronic dorsal trunk vagotomy. Light microscope autoradiographic study of the normal distribution of each of the abdominal vagal trunks in the gastric wall showed that the ventral trunk was distributed exclusively to the ventral surface of the stomach. The dorsal trunk was distributed to the dorsal surface of the stomach as well as the ventral surface of the pyloric antrum and the pylorus. Three weeks after ventral trunk vagotomy or dorsal trunk vagotomy, there was no change in the pattern of distribution of both abdominal vagal trunks. There was no tendency for compensatory spread of the surviving vagal trunk to the denervated areas of the stomach. Pre-ganglionic vagal efferent fibres reach the submucosal plexus but not the mucosa. Electron microscope analysis of vagus nerve fibre composition showed that the left and right cervical vagus nerves contain equal numbers of fibres whereas the ventral trunk contains only about 50 percent of the number of fibres in the dorsal trunk. The total number of fibres in both abdominal vagus nerve trunks is only 5 0 percent of all fibres in the cervical trunks. Thirteen percent of all fibres in the cervical vagus nerves and less than 1 percent of those in the abdominal trunks are myelinated. The vagus nerve is essentially composed of afferent fibres with only 12 percent of cervical and 7 percent of abdominal vagaltrunks being efferent. The size-frequency distribution of the myelinated fibres is unimodal with a distinct peak at 2 to 3 µm diameter. Less than 1 percent of the myelinated fibres have diameters above 8 µm. Myelinated fibres less than 1 urn diameter were seen but they form a very small percentage of all myelinated fibres. Because the myelinated fibres of the vagus nerve in the ferret have generally small diameters, and because the nerve is composed mostly of non-myelinated C-fibres, the vagus nerve in this animal is a slowly conducting nerve.en_US
dc.identifier.urihttp://hdl.handle.net/123456789/294
dc.language.isoenen_US
dc.subjectMULTIDISCIPLINARY,en_US
dc.subjectVAGUS,en_US
dc.subjectNERVE,en_US
dc.subjectCHRONIC,en_US
dc.subjectVAGOTOMYen_US
dc.titleA MULTIDISCIPLINARY STUDY INTO CHANGES IN THE VAGUS NERVE FOLLOWING PARTIAL CHRONIC VAGOTOMYen_US
dc.typeThesisen_US
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