QUANTITATIVE ASSESSMENT OF SYNAPTIC DENSITY IN THE OUTER MOLECULAR LAYER OF THE HIPPOCAMPAL DENTATE GYRUS IN ALZHEIMERS-DISEASE

We quantified the synaptic density in the outer molecular layer of the hippocampal dentate gyrus. Autopsy material from 9 individuals with A lzheimer disease (AD) were compared to 10 age-matched, postmortem-matc hed controls without dementia, using standard electron microscopy. Sta tistical analyses showed a significant change in the density of synaps es between controls and AD subjects. There was a significant decline i n the width of the entire molecular layer in the AD material. Synaptic density showed a significant correlation with synaptic apposition len gth in both AD and control groups. As the number of synapses declined, the synaptic apposition length increased. The decline in density of s ynapses in the AD group might reflect the degree of neuronal loss in t he entorhinal cortex. Such a loss in synaptic connectivity could play a key role in memory-related problems associated with AD.