1991 Fiscal Year Final Research Report Summary
Pharmacological research on biological clock
| Project/Area Number |
02660313
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
基礎獣医学
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| Research Institution | Miyasaki University |
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Principal Investigator |
NURAKAMI Noboru University of Miyazaki veterinary Physiology Assistant Professor, 農学部, 助手 (80150192)
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| Project Period (FY) |
1990 – 1991
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| Keywords | Circadian Rhythm / Suprachiasmatic nucleus / Vasopressin / Cell Culture / Photoperiod |
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| Research Abstract |
1. We have developed a dissociated suprachiasmatid nudleus(SCN)cell culture system in order to begin a cellular analysis of the mannalian circadian oscillator. Monolayer cultured neurons prepared from the SCN regions of 1 day old rat were maintained in serum-free culture medium for 3-4 weeks and then profused. In 12 out of 40 wells, a circadian oscillation of vasopressin release persisted for at least 4-5 cycles until the end of perfusion period with no damping of the amplitude. This finding suggest that cultured SCN neurons retain the capacity for circadian oscillation for a long time, and should provide a useful model for the analysis of a sawalian circadian system at the cellular level.
2. Experiments were performed to determine if the circadian clock re-entrains more quickly to an 8 hour phase shift in light-dark(LD)cycles than does the overt rhythm of activity. To investigate the re-entrainment of the clock itself to an 8 hour advance or delay in the LD cycle, ttie rats were releas
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ed into constant darkness only two or three days after a shift in LD cycle, and the amount of the phase shift of the clock itself was estimated from where freerunning rhythm started. If the circadian clock could rapidly reset itself to the new LD cycle, it was predicted that the free-running rhythm of activity would start from near the dark period of the new LD cycle rather than the preceding one. When rats were released into constant darkness three days after the LD cycle was advanced by 8 hours, the activity of the freerunning rhythm started near time of dark period of the new LD cycle. When rats(n=24)were released into constant darkness two days after the LD cycle was advanced, a half of rats started the activity near time of dark period of the new LD cycle. When rats were not released into constant darkness after LD cycle was advanced by 8 hours, it took 6.4 days for activity rhythm to re-entrain to the advanced LD cycle. These results suggest that the circadian clock itself re-entrains very rapidly following either 8 hour phase advance or delay in the LO cycle. while the overt rhythms of activity take many cycles. Less
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