This thesis addresses the role of diaphragmatic afferents in the regulation of breathing. The activation of diaphragmatic thin-fiber afferents by bradykinin, a physiological substance produced during muscle contraction, caused a stimulation and a redistribution of inspiratory motor drive, and a decrease in inspiratory time. These afferents are also involved in the regulation of airway smooth muscle tone, since tracheal tension and lung resistance decreased during electrical activation of the phrenic nerve. To mimic in vivo activation of mechanoreceptive afferents, phrenic nerve stimulation was performed during inspiration or expiration. Similar increases in inspiratory motor drive and respiratory timing occurred during inspiratory and expiratory phrenic stimulation. In addition, vagal input potentiated the stimulatory effect of inspiratory phrenic, but not tibial, nerve activation. Prolonged activation of diaphragmatic thin-fiber afferents by ischemia caused inspiratory motor drive to increase and then decrease to baseline values. These findings indicate either a depletion of neurotransmitter substance within afferent pathways, or the development of central inhibition of ventilatory drive. In summary, diaphragmatic thin-fiber afferent activity is an important modulating influence in the control of breathing.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.28960 |
| Date | January 1994 |
| Creators | Wilson, Christine R. (Christine Roberts) |
| Contributors | Hussain, Sabah N. A. (advisor), Magder, Sheldon (advisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Physiology.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001453837, proquestno: NN05813, Theses scanned by UMI/ProQuest. |
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