Physiology of avian circadian pacemakers.

Nov 1, 1979Federation proceedings

How bird internal clocks work to control daily rhythms

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Circadian Biology on OpenScience ↗PubMed ↗

Abstract

In house sparrows, removal of the pineal gland abolishes circadian rhythmicity, which is restored by transplantation of a donor's pineal gland.

The pineal gland is a critical component in the circadian rhythm system of birds.
Different bird species may rely on the pineal gland to varying degrees for maintaining circadian rhythms.
In chickens, circadian rhythms in the pineal gland are linked to rhythmic melatonin synthesis, but removal of the pineal does not disrupt their circadian rhythmicity.
Lesions of the suprachiasmatic nuclei eliminate circadian rhythms in sparrows and some other vertebrates, indicating its significant role in circadian organization.
The interactions among the pineal gland, suprachiasmatic nuclei, and potentially other brain regions may contribute to vertebrate circadian regulation.

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The pineal gland plays a cental role in the circadian organization of birds, although it is clearly only one component in a system with other components that have not yet been positively identified. The relative importance of the pineal and other components may vary from one group of birds to another. In the most thoroughly studied species, the house sparrow, pineal removal abolishes circadian rhythmicity; rhythmicity is restored by transplantation of a donor bird's pineal and the restored rhythm has the phase of the donor. This, and other evidence, argues convincingly that the pineal is a pacemaker in the sparrow circadian system. The pineal of the chicken has circadian rhythms in several biochemical parameters that result in the rhythmic synthesis of melatonin. The activity of one enzyme in this pathway is rhythmic for at least two cycles in organ culture. In view of this result it is interesting that pineal removal does not abolish circadian rhythmicity in chickens. The fact that lesions of the suprachiasmatic nuclei abolish circadian rhythms in sparrows, several mammalian species, and perhaps Japanese quail and reptiles, suggests that vertebrate circadian organization may be based on differentially weighted interactions between the pineal, the suprachiasmatic nuclei, and perhaps other brain regions.

Physiology of avian circadian pacemakers.

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