NGF and TrkA RNA oscillate in a circadian manner in the SCN and TrkB and TrkC in the liver. Mice were entrained in a 12 h light/dark cycle and were killed at 4 h intervals (n = 4 per group and genotype). A, At the indicated times, the SCN (left) and liver (right) were dissected; RNA was extracted; and the levels of NGF, BDNF, TrkA, TrkB, and TrkC were analyzed by real-time PCR. B, RNA from SCN was extracted and the level of FAS-TNFα was analyzed by real-time PCR at the indicated times. Results of at least three independent experiments with duplicate measurements are shown. Data from CT20 are double plotted. Error bars represent the SEM of the mean, where the maximum RNA amount was set to 100. CT, Circadian time.