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Neurosci Lett. 1999 Mar 26;263(2-3):125-8.

The role of inositol trisphosphate-induced Ca2+ release from IP3-receptor in the rat suprachiasmatic nucleus on circadian entrainment mechanism.

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Ishida Group of Clock Gene, National Institute of Bioscience and Human Technology, AIST, MITI, Tsukuba Science City, Japan.


Synchronization between the environmental lighting cycle and the circadian clock in the suprachiasmatic nucleus (SCN) is correlated with Ca2+ increase. The mechanism underlying the increase of Ca2+ and its relation to clock resetting are unknown. To address these issues, we examined the possibility whether inositol 1,4,5-trisphosphate receptor (IP3-R), which regulate intracellular Ca2+, was involved in the circadian rhythm component of the rat SCN. A novel IP3-induced Ca2+ release modulator, 2-amino-ethoxy diphenylborate (2APB), blocked optic nerve stimulation-induced neuronal field potentials in the SCN. Furthermore, glutamate-induced phase delay of the circadian firing pattern in the SCN was also blocked completely by 2APB in vitro. Together, these data suggest the possibility that IP3-induced Ca2+ release through IP3-R plays a role in the entrainment of the mammalian circadian clock, the SCN.

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