|Compensatory Alterations in Receptor-Stimulated Phosphoinositide Hydrolysis in the Hippocampus Vary as a Function of Dose of Colchicine.
Bonner, M. J. ;
Tilson, H. A. ;
|Health Effects Research Lab., Research Triangle Park, NC. ;North Carolina Univ. at Chapel Hill.
Endogenous substance receptors ;
Ibotenic acid ;
Dose-response relationships ;
Cerebellar nuclei ;
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The stimulation of inositol phospholipid (PI) hydrolysis by various receptor agonists was measured in the hippocampus of rats 12 weeks after various concentrations (0.5-2.0 micrograms/site) of colchicine were infused into the dentate gyrus. Colchicine produced a dose-related decrease in the average width and length of the granule cell line; the pyramidal cells in CA1 and CA3 regions of the hippocampus were affected only at higher concentrations of colchicine. Compensatory increases in receptor-mediated hydrolysis of phosphoinositides (PI) in hippocampal slices were seen at 100 micromoles carbachol and ibotenic acid in rats receiving 1.5-3.5 micrograms colchicine/site. Compensatory increases in norepinephrine (100 micromoles) and N-methyl-D-aspartate (100 micromoles) stimulated PI were seen at 2.5-3.5 and 3.5 micrograms colchicine/site, respectively. Compensatory increases in PI hydrolysis were not seen in slices from animals receiving 0.5 micrograms colchicine/site. These data support the hypothesis that the signal transduction system in the hippocampus undergoes a compensatory change following experimentally induced destruction of dentate gyrus granule cells. In addition, these changes occur for more than one neurotransmitter and the alterations vary as a function of the size of the lesion. (Copyright (c) 1991 Elsevier Science Publishers B.V.)