Circadian modulation of the ryanodine receptor type 2 in the SCN of rodents

WE examined the temporal modulation of intracellular calcium release channe ls in the suprachiasmatic nucleus (SCN). We found a circadian rhythm in [H- 3]ryanodine binding that was specific to the SCN. The peak in the rhythm oc curred at CT 7 and was due to an increase in Bmax, which correlated well wi th immunoblots showing an increase in RyR-2 expression in the SCN. Double i mmunohistochemical studies showed that RyR-2 was expressed exclusively in n eurons. Ryanodine and caffeine applied around CT 7-9 advanced the clock pha se in a hamster brain slice preparation. No rhythm of IP3R was seen in any of the brain areas studied. Our results indicate that RyR-2 exhibits an end ogenous rhythm, which influences the intracellular calcium dynamics and thu s modulates SCN activity. (C) 1999 Lippincott Williams & Wilkins.