Effect of aging in human cortical pre- and postsynaptic serotonin binding sites

Area of Science:

• Neuroscience
• Neurochemistry
• Aging Research

Background:

• Serotonin (5-HT) system alterations are implicated in aging.
• Previous studies suggest an overall age-related loss in serotonin 5-HT1 receptors.
• The specific subtypes and their changes with age require further elucidation.

Purpose of the Study:

• To investigate age-related changes in specific serotonin (5-HT) receptor binding sites and affinity in the human frontal cortex.
• To determine the contribution of different 5-HT receptor subtypes to age-related serotonergic decline.
• To assess whether cortical serotonergic innervation is affected by aging.

Main Methods:

• Simultaneous determination of 5-HT1A, 5-HT1D, and 5-HT2 binding sites and affinity.
• Measurement of serotonin (5-HT) uptake sites using [3H]paroxetine labeling.
• Analysis of frontal cortex samples from 23 control subjects across a wide age range (16-75 years).

Main Results:

• A significant reduction in the number of 5-HT1D and 5-HT2 binding sites was observed with increasing age.
• A significant decrease in 5-HT2 binding affinity was also found in relation to age.
• The density of [3H]paroxetine-labeled 5-HT uptake sites remained stable, indicating no age-associated reduction in serotonergic innervation.

Conclusions:

• The age-related decrease in serotonin 5-HT1D and 5-HT2 binding sites, particularly the 5-HT2 subtype, may account for previously reported overall 5-HT1 age-related losses.
• Cortical serotonergic innervation appears to be preserved during aging.
• These findings highlight specific serotonin receptor subtype vulnerabilities to aging in the human frontal cortex.