Pyrithiamine-induced thiamine deficiency (PTD) in the rat results in a metabolic disorder associated with selective cerebral vulnerability. The basis of the histological lesions that develop in areas that include the thalamus, medial geniculate, and inferior colliculus is undetermined but an underlying glutamate-mediated form of excitotoxicity may be responsible. This work examines the possibility that PTD leads to changes in extracellular glutamate concentration, membrane polarization status, and gene expression consistent with a decreased ability to maintain homeostatic integrity. / At the acute symptomatic stage, extracellular glutamate by concentration as determined microdialysis was found to be elevated in the thalamus but within normal limits in the non-vulnerable parietal cortex. This result suggests an involvement of glutamate in the pathogenesis of thiamine deficiency lesions. An in vivo examination of L-type voltage-sensitive calcium channel activity using quantitative autoradiography and ($ sp3$H) -nimodipine at the same stage of PTD revealed that increased activity was present in and localized to the thalamus, but was absent in areas resistant to histological damage. The finding indicates a likelihood of regional depolarization. Finally, induction of the proto-oncogene c-fos was detected in the thalamus and inferior colliculus with quantitative in situ hybridization analysis at the acute symptomatic stage, thereby confirming the association of PTD with depolarization-related events occurring in advance of the appearance of frank infarction. / Together, these results suggest that vulnerability in the thalamus may be determined by an inability to maintain spatial buffering of extracellular glutamate under energy-compromised conditions. Such an environment may be sufficient to set into motion event cascades in these cells that lead to the demise of the structure as a whole.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.28776 |
| Date | January 1995 |
| Creators | Hazell, Alan Stewart |
| 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 Neurology and Neurosurgery.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001441233, proquestno: NN05720, Theses scanned by UMI/ProQuest. |
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