1996 Fiscal Year Final Research Report Summary
Circadian Rhythms in the Function of Central Serotonin Receptors
| Project/Area Number |
07671077
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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 |
Psychiatric science
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| Research Institution | Oita Medical University |
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Principal Investigator |
NAGAYAMA Haruo Oita Medical University School of Medicine, Associate Professor, 医学部, 助教授 (70100899)
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| Project Period (FY) |
1995 – 1996
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| Keywords | SEROTONIN RECEPTOR / CIRCADIAN RHYTHM / 8-OH-DPAT / DOI / SEROTONIN SYNDROME / HYPOTHERMIA / ENDOGENOUS RHYTHM |
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| Research Abstract |
1. Circadian rhythm in the behavioral responsiveness to the selective serotonin (5-HT) 1A receptor agonist 8-OH-DPAT was studied in rats.
(1) Rats were SC injected with 8-OH-DPAT at different times of day. As a result, circadian thythm was found in behavioral (5-HT syndrome) response to 8-OH-DPAT.
(2) Circadian rhythms were investigated in the behavioral responses to intracerebroventricular administration of 8-OH-DPAT in rats. The results indicated the existence of circadian rhythms of a similar pattern to those observed in the behavioral responses to SC administration of the drug. These observations suggest that the central postsynaptic 5-HT1A receptor exhibits a circadian rhythm in its function.
(3) The 8-OH-DPAT-induced behavioral syndrome was examined in rats kept under continuous dark (DD) conditions for six days. The results revealed a circadian rhythm in the behavioral response to 8-OH-DPAT under DD conditions. The pattern of this rhythm was similar to that observed under the light-dark conditions. These results strongly suggest that the rhythm in the function of central 5-HT1A receptors is driven by the endogenous oscillator.
(4) The rhythm was examined in the responsiveness to 8-OH-DPAT by observing hypothermia. The hypothermic response displayd significant circadian rhythms. The waveform of the rhythms observed was similar to that of the rhythms in the 5-HT syndrome. The evidence further supports that the central postsynaptic 5-HT1A receptor function exhibits a circadian rhythm.
2. The circadian rhythm was investigated in the behavioral response to the SC administration of selective 5-HT2A/2C receptor sgonist DOI.A circadian rhythm was observed in the DOI-induced wet-dog shake response. Intracerebroventricular administration of DOI suggested the similar results. These results suggest that the function of the central 5-HT2A receptor exhibits a circadian rhythm.
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