Figure 1.

Rhythms of food intake and wheel running in wild-type and Vipr2^−/− mice fed ad libitum. A, B, Representative profiles of locomotor activity in wild-type (A) and Vipr2^−/− (B) mice are presented in double-plotted format. Periods of darkness are shaded. For the first 16 d, animals were exposed to a 12 h LD cycle (darkness from 7:00 P.M. to 7:00 A.M.). From day 17, animals were maintained in constant darkness. C–F, Cumulative wheel running counts (C, D) and food intake (E, F) were monitored in wild-type (black bars) and Vipr2^−/− (gray bars) mice over 4 h periods for 48 h in LD (C, E) or 2 d after transfer into DD (D, F). Values represent mean ± SEM; n = 8. The bars at the top indicate the dark period in black and the light period in white (C, E) or subjective night in black and subjective day in gray (D, F). *p < 0.05; **p < 0.01; ***p < 0.001 compared with Vipr2^−/−.