| Budget Amount *help |
¥6,900,000 (Direct Cost: ¥6,900,000)
Fiscal Year 1986: ¥1,200,000 (Direct Cost: ¥1,200,000)
Fiscal Year 1985: ¥5,700,000 (Direct Cost: ¥5,700,000)
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| Research Abstract |
Photoperiodic regulation of plasma melatonin levels in intact or pinealectomized chicken was studied to elucidate the role of pineal gland in circadian rhythm of the chicken. Under a 14L:10D photoperiod, a circadian rhythm in plasma melatonin disappearred in pinealectomized chickens (pinealectomized at 1 day of age) at 16, 29, 65 and 100 days of age, whereas the rhythm was always observed either in intact or sham-operated chickens at corresponding ages. When 14-day-old cockerels and pullets, which had been kept under a 12D:12L photoperiod, were shifted to a 12L:12D photoperiod, a circadian plasma melatonin rhythm disappered in the first dark period, but resumed in the second dark period. When the cockerels which had been kept under a 12L:12D photoperiod, were shifted to a 12D:12L photoperiod, the first nocturnal rise of plasma melatonin appered in the second dark period in a reduced magnitude, and in the third dark period in a greater magnitude. When 82-day-old pullets, which had been kept under a 12D:12L photoperiod. were shifted to a 12L:12D photopriod, plasma melatonin rise was observed in the first dark time. Similar results were observed in the photoperiodic shift in 450-day-old pullets. These results indicate the decrease in the strength of memory for circadian light-dark rhythms with advancing age in the chicken.
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