Age-related decrease of serotonergic fibres and S-100 beta immunoreactivity in the rat dentate gyrus.

The age-related changes of serotonergic fibres and S-100 beta-positive astrocytes in the rat dentate gyrus were examined using immunohistochemistry. A significant reduction in the number of the serotonergic fibres and S-100 beta-positive astrocytes was observed throughout the dentate gyrus of the aged rat. A positive correlation was noted between the decrease of serotonergic fibres and S-100 beta-positive astrocytes in the aged rat dentate gyrus. These findings support the hypothesis that the age-related degeneration of serotonergic fibres in the dentate gyrus is caused by the decrease in serotonergic neurotrophic factor S-100 beta in the astrocytes.