Fig. 6

Time-dependent suppression of locomotor activities by light pulses. Light pulses (300 lux, 2.5 h) were administered to WT mice (N = 6) and PK2−/− mice (N = 6) at ZT14, ZT16 and ZT19. The percentage of activity suppression was calculated by comparing to the locomotor activities of the corresponding periods without light pulses. Light pulses significantly inhibited the locomotor activities of WT mice delivered at all three time points (P < 0.001, P < 0.001, and P < 0.01 for ZT14, ZT16, and ZT19, respectively, paired t-tests), but with decreasing degree of suppression (ZT14 vs ZT16, P < 0.001, ZT16 vs ZT19, P < 0.05, paired t-tests). Light pulses only significantly inhibited the locomotor activities of the PK2−/− mice when delivered at ZT14 (P < 0.05, paired t-test)