Abstract
Age-related changes in synaptic density were quantitated in the prefrontal cortex of nine Macaca mulatta from 7 to 28 years of age. Ultrastructural and light microscopic observations were made on synapses stained with ethanolic phosphotungstic acid and dendritic spines impregnated by the Golgi method, respectively. Ultrastructural analysis revealed the mean synaptic density of 8.77 × 10 8/mm 3 in the cortex of six adult M. mulatta between 7 and 20 years of age. In contrast, the synaptic density of the three oldest M. mulatta, between 27 and 28 years of age, was 6.93 × 10 8/mm 3. Age-related decline in synaptic density was also evidenced by light microscopic quantitation of dendritic spines. The spine density of the three oldest M. mulatta was 0.72/μm, significantly lower than 0.98/μm found in the six young-adult M. mulatta. The data obtained in this study also suggest that the loss of synapses of the cortical neuron is not confined to any one particular segment of the dendrites.
Published Version
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