Gene Activity and Neurodegeneration in the Extrapyramidal System: A Progress Report on Molecular and Morphological Correlates
Functional neuronal plasticity and synaptic remodelling appear to be consistent feature of aging brain (Coleman et al., 1986). However, even in the absence of overt neuropathology, heterogeneous atrophic changes may occur in the brain with advancing age, suggesting differential mechanisms on specific brain regions, even in the same anatomical structure. For example hippocampal dentate granule neurons apparently remain intact and show hypertrophy of dendritic processes and increased perikaryal size in the aged brain (Coleman and Flood, 1987). Nonetheless many others e.g., pyramidal neurons of the hippocampus (Ringborg 1966) and cerebral cortex (Peters et al., 1987) show reduced perikaryal RNA content and decreased size of their perikarya, nuclei, or nucleoli. In addition, the nucleolar shrinkage is less in human locus ceruleus (LC) than substantia nigra (s.nigra) neurons (Mann and Yates, 1979), further confirming the cellular selectivity of changes. These studies support the general concept that age-related neuronal atrophic changes is not an universal or inevitable characteristic of the senescence, but may be brain region, cell type, and species specific.
KeywordsTyrosine Hydroxylase Atrophic Change DAergic Neuron Striatal Lesion Neurotoxic Lesion
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