Roles of the pineal gland and eyes on the formation of photoperiodic rhythms in the activity and biological functions of the chicken and the quail.

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This experiment was undertaken to examine the potentiality of noise as a Zeitgeber on melatonin rhythm of the immature chicken under constant darkness. Under a continuous white noise condition, both selatonin concentrations in the pineal gland and the plasma did not form daily rhythms with a peak during the experimental period. Under a 12hr white noise condition and a 12hr cockerel's calling, selatonin concentrations in the pineal gland showed clear daily rhtyhes with peaks at mid-noise-on time and sid-noise-off time. respectively. Chickens recognized the condition with a white noise as a subjective night, and the condition with a cockerel's calling as a subjective daytime, suggesting communications among chickens are iill>ortant for forming a rhythm, and noise may act as a Zeitgeber for forming circadian rhythms of melatonin under constant darkness in the chicken. Next experiment was conducted to elucidate the effects of pinealectogy and/or blind on plasma selatonin rhythms of immature, -chickens. The plasma melatonin concentrations of intact and sham-pinealectonized chickens showed a prominent daily rhythm with a peak at sid-scotophase. In either pinealectonized or blinded(by complete bilateral orbital enucleation)chickens, plasma melatonin concentrations showed daily rhythms with a small fluctuation compared with a intact and sham-operated chickens. But in both pinealectonized and blinded chickens, no plasma melatonin rhythm detected. These results indicated that the plasma melatonin rhythm is controlled by the melatonin secretion from both pineal and retina in young chicks, and that the rhythm is mainly controlled by the secretion fros pineal but not by that from eyes with advancing age. Furthermore, when the chick just after hatching was pinealectonized. eyes in place of the pineal gland mainly induced to selatonin rhythm in the plasma.