In anesthesia practice, consciousness is often equated with the waking state and with the ability to respond to stimuli in the integrated manner. The reversible loss of consciousness is induced by the general anesthetic, which have a wide range of molecular structure and physicochemical characteristics. The mechanisms of unconsciousness induced by anesthetic agents are not well understood. The studies I have conducted for my Ph.D. have focused on how anesthetic drugs produce unconsciousness in human subjects. In two separate PET studies, receptor imaging and regional CBF analysis were used to examine the unconsciousness induced by propofol, a popular general anesthetic. The first study evaluated kinetic analysis methods for estimation of the receptor availability of the muscarinic receptor using dynamic positron emission tomography (PET) studies with [N-11C-methyl]-benztropine. The study also investigated the effect of propofol on central muscarinic receptor availability during general anesthesia. The results of this study suggested the propofol-related reductions in muscarinic receptor availability. The second study identified the brain function changes specifically linked to the difference in levels of consciousness. We used physostigmine (an anticholinestherase) to restore consciousness in the subjects anesthetized with a constant concentration of propofol. The results revealed that the thalamus and precuneus/cuneus jointly play a critical role in controlling the changes in the level of consciousness during general anesthesia. / Together, these two studies support a hypothesis that the joint deactivations of a Common Midline Core, which includes the medial thalamus, midline precuneus/cuneus, prefrontal cortex and other related cortical areas, contribute to the unconsciousness induced by general anesthetics. These deactivations are mediated, at least partially, by a reduction in the central cholinergic transmission.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.102770 |
| Date | January 2006 |
| Creators | Xie, Guoming, 1963- |
| 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 (Division of Neuroscience.) |
| Rights | © Guoming Xie, 2006 |
| Relation | alephsysno: 002541513, proquestno: AAINR27858, Theses scanned by UMI/ProQuest. |
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