Loss of [3H]kainate and of NMDA-displaceable [3H]glutamate binding sites in brain in thiamine deficiency: Results of a quantitative autoradiographic study |
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Authors: | Christine Peterson Maryse Héroux Joel Lavoie Dr. Roger F. Butterworth |
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Affiliation: | (1) Dept. of Gerontology, University of Southern California, Los Angeles, California;(2) Clifical Biochemistry Service, Hôpital Saint-Luc (University of Montreal), Montreal, Quebec, Canada;(3) Neuroscience Research Unit, Hôpital Saint-Luc (University of Montreal), 1058 St-Denis St., H2X 3J4 Montreal, Quebec, Canada |
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Abstract: | Previous studies suggest that alterations of brain glutamate synthesis and release occur in experimental thiamine deficiency. In order to assess the integrity of post-synaptic glutamatergic receptors in thiamine deficiency, binding sites for [3H]glutamate (displaced by NMDA), [3H]-kainate, and [3H]quisqualate (AMPA sites) were evaluated using Quantitative Receptor Autoradiography in rat brain following 14 days of treatment with the central thiamine antagonist pyrithiamine. Compared to pair-fed controls, brains of symptomatic thiamine-deficient animals contained significantly fewer NMDA-displaceable binding sites in cerebral cortex, medial septum and hippocampus. It has been suggested that NMDA-receptor mediated glutamate excitotoxicity plays a role in the pathogenesis of neuronal loss in thiamine deficiency. If such is the case, the selective loss of NMDA binding sites in cerebral cortex and hippocampus offers a possible explanation for the relative nonvulnerability of these brain regions to pyrithiamine-induced thiamine deficiency. [3H]quisqualate (AMPA) binding sites were unchanged in all brain regions of pyrithiamine-treated rats whereas [3H]kainate sites were significantly reduced in density in medial and lateral thalamus. The decline in these binding sites may be due to neuronal loss in pyrithiamine-induced thiamine deficiency. Alterations of glutamatergic synaptic function involving both NMDA and kainate receptor subclasses could contribute to the pathogenesis of neurological dysfunction in Wernicke's Encephalopathy in humans. |
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Keywords: | Thiamine deficiency glutamate NMDA receptors AMPA receptors kainate receptors autoradiography |
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