Ageing of the human entorhinal cortex and subicular complex

Abstract

Age-dependent changes in the entorhinal cortex (EC) and subicular complex (SC) were studied in 30 brains of patients who died between 14 and 86 years of age, without CNS impairment, as determined by macro- and microscopic examination. The brains were fixed in 10% formalin and embedded in paraffin. Three series of corona1 EC and SC sections (7 pm) were stained by Nissl, PAS or hematoxylin-eosin. Using neuronal count and Kariometry, age-dependent modifications were studied in layers 11, 111 and V of the lateral area of the EC; in the pyramidal layer of the subiculum (S), and in layer 11 of the presubiculum (PS). Al1 EC layers studied presented a slight (11-20%) although significant reduction up to 35 years, but from 35 to 75 years the decrease was not significant. After 75 years the neuronal loss increased slightly. The nuclear area decreased up to the age of 40-45 years, (10-18%) and augmented from this age up to 75 years (10-14%). During the last period of life, the nuclear area did not change. From 30-60 years, pyramidal layer in the S showed a significant neuronal loss (30%), thereafter, neuronal reduction was less. At early years, the nuclear area decreased insignificantly (15%), and from 35 years up to the most advanced age studied, it increased significantly (13%). In the PS, layer 11 manifested a cell loss throughout the lifespan (32.9%) and the changes in the nuclear area did not reach statistical significance due to the dispersions of its values. These results lead to the conclusion that the neuronal loss in EC is notably less than in S and PS and, in general, than in other centres. The sequence of neuronal loss is also different in the EC and in the S. While in EC the maximal loss occurs up to 35 years of age, in S the most pronounced loss begins precisely after this age.