Ageing of the brain is manifested by cognitive decline. For many years, this decline in the most important of brain functions was associated with neuronal loss, as it was believed that senescence is inevitably associated with neuronal death. Recent investigations, however, have shown that physiological brain ageing (i.e. in the absence of evident neurodegenerative pathology) is not associated with appreciable neuronal loss. On the other hand, glial cells are affected in physiological brain ageing. In astrocytes, advanced age initiates conditions similar to a mild reactive gliosis. Astroglial cells from old brain have higher expression of GFAP and the glial calcium binding protein S100. There are some indications that the number of astrocytes in aged brain can be increased by as much as 20 per cent, although these estimates require more precise definition. Overall, numbers of oligodendrocytes and microglia are not changed in aged brain, although the number of activated microglial cells is significantly increased.
Was this article helpful?