Age-related changes in ionized calcium-binding adapter molecule 1 immunoreactivity and protein level in the gerbil hippocampal CA1 region

Microglia are evenly distributed throughout the brain parenchyma. They respond rapidly to a variety of alterations in the microenvironment of the brain and act as sensors for pathological events in the brain. In the present study, we investigated the age-dependent changes in the immunoreactivity and protein level of ionized calcium-binding adapter molecule I (lba-1), a microglial marker, in the CA1 region of the gerbil hippocampus. lba-1 immunoreactive microglia were detected in the hippocampal CA1 region of the postnatal month I (PM 1) group. lba-1 positive microglia were morphologically inactive between the PM I and PM 12 stages. Some lba-1 immunoreactive microglia were present in the active form in the hippocampal CA1 region of the PM 18 and PM 24 groups. The lba-1 protein levels in hippocampal CA1 homogenates were decreased in the PM I through PM 6 groups and increased in an age-dependent manner thereafter. These results suggest that Iba-1 immunoreactive microglia in the active form were detected in the hippocampal CA1 region in the PM 18 and PM 24 groups. This result may be associated with an age-dependent susceptibility to neurodegenerative diseases associated with the hippocampus.