Age-related changes in the subiculum of Macaca mulatta: synaptic density

Area of Science:

• Neuroscience
• Neurobiology
• Aging Research

Background:

• Dendritic spines and synapses are crucial for neuronal communication and plasticity.
• Understanding age-related changes in neuronal structure is vital for comprehending cognitive decline.

Purpose of the Study:

• To investigate age-related changes in dendritic spine and synaptic density in the subiculum of Macaca mulatta.
• To quantify structural differences in specific dendritic foci across different age groups.

Main Methods:

• Golgi-Cox staining was used to analyze dendritic spines in six distinct dendritic foci of pyramidal neurons.
• Electron microscopy with ethanolic phosphotungstic acid staining assessed synaptic density.
• Quantification was performed on young (7-12 years), middle-aged (18-21 years), and old (29 years) rhesus monkeys.

Main Results:

• No significant difference in spine density was observed between young and middle-aged animals.
• Old animals exhibited significantly lower dendritic spine density (0.87/microns) compared to young (1.09/microns) and middle-aged (1.15/microns) groups.
• Synaptic density also declined significantly in old animals (8.3 x 10^8/mm3) versus young (9.5 x 10^8/mm3) and middle-aged (10.2 x 10^8/mm3) groups, affecting all dendritic regions equally.

Conclusions:

• Aging in Macaca mulatta is associated with a significant reduction in both dendritic spine and synaptic density in the subiculum.
• The observed loss of synapses and spines occurs uniformly across different dendritic compartments.
• These findings highlight structural correlates of aging in the primate brain, particularly within the subiculum.