FIG. 4.

Rhythmic gene expression in the SCN, as assessed by in situ hybridization. Significant rhythms of expression of mPer1, mPer2, mCry1, and Bmal1 were detected in both wild-type and mPER3-deficient mice, and there were no differences between the genotypes. mPer3 RNA levels were significantly reduced in the SCN of mPer3-deficient mice. Each value represents the mean ± standard error of the mean for six to eight mice. Adjacent sections from the same group of mice were used for all probes. Tissues were collected on the first day in DD. The horizontal bar at the bottom of each panel represents the lighting cycle that the animals experienced prior to entry into DD: subjective day is gray, and subjective night is black. (Circadian times 0 and 12 represent the times at which the lights would have been turned on and off had the animals remained in LD.) Data from circadian times 3, 21, and 24 are double plotted.