| Budget Amount *help |
¥2,800,000 (Direct Cost: ¥2,800,000)
Fiscal Year 2006: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 2005: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 2004: ¥1,100,000 (Direct Cost: ¥1,100,000)
|
|---|
| Research Abstract |
In mammals, circadian rhythms are driven by a pacemaker located in the suprachiasmatic nuclei (SCN) of the hypothalamus. The pacemaker is composed of an ensemble of multiple, single-cell oscillators in the SCN. Isolated SCN shows clear circadian oscillation in release of arginine vasopressin (AVP) in organotypic slice cultures. When the ventral part was removed by a surgical cut across the slice in the horizontal plane, the period became shorten On the other hand, the removal of the dorsal part did not affect period length. When the rostral, central and caudal SCN were cultured separately, the rostral and caudal parts of the SCN showed shorter periods than central SCN. Therefore, it is suggested that the shorter periodic region is located in a shell, a subdivision composed predominantly of AVP cells, and their rhythm is synchronized to a core region, a subdivision composed of vasoactive intestinal polypeptide (VIP) cells. Immunohistchemical analysis of the slice showed that proportions of VIP-positive region in the SCN are smaller in the slices which showed shorter periods. In the slice contains core region, furthermore, the applications of VIP antagonist shortened the periods of the AVP releasing rhythm. These data indicate that the oscillators in AVP cells have short periods and are entrained by VIP cells to form a single integrated rhythm. In slice cultures, pulse application of NM DA, an agonist of glutamate, induced light pulse-type phase shifts in AVP releasing rhythm. In dissociated cell cultures, however, VIP but not glutamate induced the phase shifts. NMDA-induced phase shifts in slice cultures were attenuated in the presence of VIP antagonist. These data indicate that photic information entrain VIP cells at first and then VIP cells entrain AVP cells. Together with all findings, it is suggested that core part of the SCN would regulate the shell part by VIP.
|
