| Research Abstract |
Age-related changes in various circadian rhythms have been documented. However aging mechanisms in circadian system is still unknown. To clarify the role of suprachiasmatic nucleus (SCN) in correlation between aging mechanism and circadian system, we adapted the analyzes of circadian locomotor activity and the quantitative immunohistochemistry. 1) .Male Sprague Dawley rats (SD) and diabetes insipidus (DI) rats were divided into three groups ; 2-5,12-16 and 18-30 months age. Zitter rat (zi), which shows central spongy degeneration, divided two groups (1-3 and 7-10 months age). The circadian locomotor activity (LMA) was measured by infra-red area sensor. The free-running period under constant dark shortened with age in all strains. Two hours light pulse caused the phase shift depending on the applied circadian time in young SD rat, but not in old SD,DI and 7-10 months zi rat. In old SD rats, the re-entraining days to reverse lighting schedule postponed with age. These aging effects of 7-10 months zi rats were equivalent with over 24 months SD rats. 2).The Fos-like immunoreactive (Fos-IR) cells was diffusely located in SCN.Greater amount of Fos-IR cells were seen in light phase than dark phase under light-dark condition. This change was disrupted in old rat. Light induced Fos-IR cells were confined in the ventrolateral part of SCN during constant dark, and were expressed more in subjective night than day. This change did not show any difference with the age. These results suggest that a part of aging mechanism in circadian rhythm due to the disruption of transduction from circadian oscillator, and the signal transduction from retina is not affected by aging.
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