|Budget Amount *help
¥2,000,000 (Direct Cost : ¥2,000,000)
Fiscal Year 1995 : ¥900,000 (Direct Cost : ¥900,000)
Fiscal Year 1994 : ¥1,100,000 (Direct Cost : ¥1,100,000)
1.We compared the circadian oscillation of melatonin release from cultured pineal cells in Japanese quail, pigeon and house sparrowin vitro. Melatonin release increased during the dark period and low during the light period in all pineal cell cultures. Under DD conditions, the circadian rhythm of melatonin release persisted for up to 3-4 cycles in pigeon and house sparrow pineal cells, but not Japanese quail cell. These results strengthen the argument that the avian pineal gland's role in circadian organization differs between species.
2.Six-hour pulses of anisomycin, an inhibitor of 80S ribosomal protein synthesis, induced steady atate and phase-dependent phase shifts of the circadian oscillation of melatonin release. The phase advances and delays occurred at circadian time (CT) 7.9h and between CT18.6 and 4.5h, respecitively. Furthermore, anisomycin blocked the light-induced phase advance. These results suggest that 80S ribosomal protein synthesis is involved in the normal and light-e
ntrainment functions of the circadian oscillator in pigeon pineal cells.
3.When blind rats were transferred from a cage with a running wheel to a cage without a running wheel, the tau of free-running rhythm lengthened. A complete lesion of the IGL lengthened the tau of the wheel-running activity rhythm, but not, locomotor activity rhythm. When IGL-lesioned rats were transferred from a cage with a running wheel to a cage without a running wheel, no further change was observed. These results indicate that the tau of the free-running rhythm is modified by a daily activity of wheel-running, but not by locomotor activity, and that the IGL may be involved in this modification.
4.We examined whether continuous melatonin administration through subcutaneously implanted silastic tubing accelerates reentrainment of circadian rhythms of locomotor activity to shifted illumination cycles, and found that rats required less time to reentrain to an advance or delay phase shift of a light-dark cycle while carrying a silastic implant filled with melatonin than while carrying an empty implant. These results suggest that continuous administration of melatonin accelerates reeentrainment of the circadian locomotor activity rhythm to a new light-dark cycle.