Early onset and topographical distribution of hypertrophied astrocytes in hippocampus of aging rats: a quantitative study.

Our results indicate that the density of astrocytes exhibiting hypertrophy in the hippocampus increases dramatically and progressively with age, being significantly elevated even in mid-life (13 month) animals. However, the total population of astrocytic cells (hypertrophied and nonhypertrophied) in the quantified region is not significantly elevated. Further, the relative distributions of both hypertrophied and total glial cells remained remarkably constant at the three ages measured. Reactive hypertrophy of astrocytes therefore appears to occur "in place" and migration of astrocytes does not appear to be a major factor in the hippocampus during aging. Of particular note was the finding that astrocyte hypertrophy is far more prominent in synaptic terminal fields than in myelinated fibers of the same system.