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      The pineal and melatonin: Regulators of circadian function in lower vertebrates

      Experientia
      Springer Nature

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          Circadian organization in lizards: the role of the pineal organ

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            A circadian oscillator in cultured cells of chicken pineal gland.

            T Deguchi (1979)
            The activity of serotonin N-acetyltransferase, the key enzyme of melatonin synthesis, shows a marked circadian rhythm in the pineal glands of various animal species. The regulation mechanism of the N-acetyltransferse rhythm in birds is different from that in mammals. N-Acetyltransferase activity in rat pineal gland is controlled by the central nervous system through the sympathetic nerves from the superior cervical ganglion, while in chicken the endogenous oscillator for N-acetyltransferase rhythm is presumably located in the pineal gland. Recently it has been shown that N-acetyltransferase activity oscillates in a circadian manner in the organ culture of chicken pineal glands. When chicken pineal glands were organ-cultured under continuous illumination, the nocturnal increase of enzyme activity was suppressed. These observations suggested that chicken pineal gland contains a circadian oscillator, a photoreceptor and melatonin-synthesising machinery. A central question arises whether the circadian oscillation of N-acetyltransferase activity and its response to environmental lighting are generated within the cell or are emergent properties of interaction between different types of pineal cells. I report here that in the dispersed cell culture of chicken pineal gland, N-acetyltransferase activity exhibits a circadian rhythm and responds to environmental lighting in the same manner as in the organ culture.
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              Role of the suprachiasmatic nuclei in the circadian system of the house sparrow, Passer domesticus.

              The suprachiasmatic nuclei (SCN) of the hypothalamus are necessary for the persistence of free running circadian activity rhythms in house sparrows. Suprachiasmatic lesions abolish circadian locomotor rhythms in constant darkness. The locomotor activity of lesioned sparrows was analyzed with two different power spectral analysis methods and was found to be arrhythmic. There was a weak correlation between the extent of damage to the SCN and the relative amplitude of the power spectral density in the circadian frequency range. In light-dark cycles (LD 12:12), the locomotor behavior of lesioned sparrows was rhythmic and similar to that of intact birds. However, entrainment was disrupted in SCN-lesioned sparrows exposed to a short photoperiod light cycle (LD 1:24). These results demonstrate that the SCN are crucial for the generation of overt circadian rhythmicity in birds. The fact that SCN lesions abolish circadian rhythms in sparrows and several mammalian species suggests that vertebrate circadian organization may be based on differentially weighted interactions among the pineal, the SCN, and perhaps other brain regions.
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                Author and article information

                Journal
                Experientia
                Experientia
                Springer Nature
                0014-4754
                1420-9071
                October 1989
                October 1989
                : 45
                : 10
                : 914-922
                Article
                10.1007/BF01953048
                2bf92560-edec-458d-818a-ad80d1f4fba5
                © 1989
                History

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