Figure 1. Circadian profiles of clock-related genes in the submandibular glands. Six-week-old male C57/BL6 mice were housed under 12:12-hour LD conditions for 19 days, and were killed at the indicated zeitgeber time (ZT: lights on at ZT0, lights off at ZT12)) on day 20. Total RNA was isolated from the submandibular glands and subjected to real-time RT-PCR analysis. Per1, Per2, Cry1, Bmal1, Dec1, Dec2, Dbp, and Reverb mRNA levels (mean ± SEM, n = 3) were determined. P-values were calculated by one-way ANOVA analysis. Expression profiles of Per1, Per2, Cry1, Bmal1, Dec1, Dec2, Dbp, and Reverb were rhythmic. To examine the effect of starvation on Cry1 expression, we withheld foods for 26–46 hrs from ZT0 on day 19 (a dotted line).