Morphometric analysis of the age-related changes of synaptophysin immunoreactivity in the human parahippocampal region

Abstract Introduction The aim of our research was to quantify the synaptic density in the parahippocampal region of the brain with densitometric measurements of synaptophysin immunoreactivity in cases of different ages. Methods The study was performed on post mortem obtained right parahippocampal region (PR) samples of 14 cadavers (10 males, 4 females) whose ages ranged from 35 to 80 years. The samples were classified into three age groups (I: 30–49; II: 50–69; III: 70 and older). The tissue was immunohistochemically processed and stained with an anti-human synaptophysin antibody. The densitometric analysis included measurement of the mean and median optical density (OD) of the PR gray and white matter (WM) digital images. This was performed with ImageJ. Results The histological analysis showed that the neuropil of the PR's layers showed two types of synaptophysin positive reactions. The first type was characterized by the presence of a granular pattern of synaptophysin immunoreactivity, and this was less intense in the second type. The synaptophysin immunopositivity of the PR gray matter neuropil decreased with age, especially in its superficial layers. The results of the densitometric analysis confirmed the significant decrease of the gray matter mean and median OD during aging. A One Way ANOVA showed that only the mean and median optical densities of the third age group were significantly lower than the values for the first age group. Discussion The synaptic density decreases with age in the PR, but this decrease is significant only in cases older than 70 years.