1997 Fiscal Year Final Research Report Summary
Analysis of circadian clock mechanism in birds and mammals.
| Project/Area Number |
08660367
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Basic veterinary science/Basic zootechnical science
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| Research Institution | MIYAZAKI UNIVERSITY |
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Principal Investigator |
MURAKAMI Noboru Miyazaki Univ.Fac.Agriculture Associate Proferssor, 農学部, 助教授 (80150192)
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| Project Period (FY) |
1996 – 1997
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| Keywords | circadian rhythm / Biological clock / pineal gland / Melatonin / suprachiasmatic nucleus |
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| Research Abstract |
Melatonin release by chick cultured pineal cells increases during the dark periods and decreases during the light periods under light-dark cycles, and this rhythmic secretion is maintained under constant conditions, with a period close to 24h. The mechanisms how circadian oscillator drives the melatonin rhythm under constant conditions have not been elucidated enough. We examined the possibility that cyclic AMP-dependent protein kinase. A is involved in the subjective nocturnal increase in melatonin release by chick pineal cells cultured under constant darkness. The subjective nocturnal increase of melatonin release was suppressed dose-dependently by H8 (protein kinase inhibitor) and H89 (specific protein kinase A inhibitor), but not by calphostin C (specific protein kinase C inhibitor) in static cell cultures. In a cell perfusion experiment, 9 hour pulses of H8 and H-89 starting at ZT 9 (CT 11.2) h suppressed the subjective nocturnal increase in melatonin rhythm in dose-dependent manner without causing a phase shift. An intracellular Ca2+ chelator, BAPTA-AM,and extracellular Ca2+ chelators, BAPTA and EGTA,suppressed both the subjective nocturanal increases in melatonin release and cAMP levels dose-dependently. These direct evidences strongly support the hypothesis that cAMP-dependent protein kinase A may be involved in the subjective nocturnal increase in melatonin release by chick pineal cells, and that intracellular Ca2+ plays an important role in pineal adenylate cyclase activation.
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