Calbindin expression in the hamster SCN is influenced by circadian genotype and by photic conditions

CIRCADIAN rhythmicity in mammals, is controlled by the suprachiasmatic nucl ei (SCN) of the hypothalamus. We previously described a discrete subnucleus in the core of the hamster SCN containing calbindin-D-28k-positive cells w hich are fos-positive in response to a light pulse. Ablation of this subnuc leus results in loss of circadian locomotor rhythmicity even when other par ts of the SCN are spared. Here we show that Tau mutant hamsters have signif icantly more calbindin-D-28k in the SCN than do wild type hamsters, and tha t SCN calbindin-immunoreactivity in the SCN increases in the dark. This is correlated with changes in magnitude of light mediated phase shifts in loco motion. The data are consistent with a role for calbindin cells in light me diated entrainment and phase shifting. (C) 1999 Lippincott Williams & Wilki ns.