| Budget Amount *help |
¥2,200,000 (Direct Cost: ¥2,200,000)
Fiscal Year 1995: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 1994: ¥1,400,000 (Direct Cost: ¥1,400,000)
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| Research Abstract |
In the present experiment, using an in vivo microdialysis technique and an in vitro organotypic slice culture of the suprachiasmatic nucleus (SCN), we measured circadian rhythm of some neuropeptides and response to light or drugs in the rat SCN.
In in vivo experiment, extracellular concentrations of glutamate and aspartate were measured in the vicinity of rat SCN by means of in vivo microdialysis. The concentration of both excitatory amino acids (EAAs) were higher during the dark phase than during the light under the light-dark cycle. When rats were released into the complete darkness, the 24-h pattern in the aspartate continued at least for one cycle. The nocturnal increase in the EAA levels were not due to the increase of locomotor activity during the night time, because the 24-h rhythms were also detected in animals under urethan anesthesia. A 30-min light pulse given either at ZT 1 or ZT 13 elevated the EAA levels during the latter half of the light pulse, except the glutamate by a
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pulse at ZT 1. The extracelluar EAA levels in the vicinity of the rat SCN showed the circadian rhythm with a nocturnal peak and increased in response to the continuous light and brief light pulse.
In in vitro experiment, the slices of the SCN were obtained from 7,8-day-old rats and cultured individually in tubes on a roller drum for 14 ddays. The vasoactive intestinal polypeptide (VIP) amount in the medium of SCN culture showed a circadian rhythm withe a-22-h period. Circadian rhythm with identical periods were also observed in arginin-vasopressin (AVP) amount of the same culture. Circadian rhythms in the release of AVP and VIP were measured simultaneously and logitudinally. The phase relationship between the two peptide rhythms was relatively constant in the culture without a treatment of antinitotic drugs but became diverse reduce the number of glial cells. By monitoring the two rhythms continuously for 6 days, different periods were detected inculture with the antimitotic treatment. Furthermore, N-methyl-D-aspartate (NMDA) shifted the phase of the two peptide rhythms in the same culture defferently. These results indicate that the AVP and VIP release are under control of different circadian oscillators. Less
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