SCN lesions eliminate circadian rhythms of peripheral gene expression in liver and kidney of control (nonparabiotic) mice. Mean (±SEM) expression of mPer1, mPer2, and mBmal1 (relative to GAPDH) in liver and kidney of intact or SCN-lesioned mice killed on the third day of constant darkness at ZT1 (white bars) or ZT13 (black bars) is shown. ZT1 values differed significantly from those at ZT13 in intact, but not in SCN-lesioned, mice (*, P < 0.05).