Figure 5.

Effect of a 5 h phase advance on activity initiation in Mc3r−/− mice and WT mice. WT and Mc3r−/− littermates were placed into wheel running cages and physical activity was monitored in 6 min bins/24 h. A, Averaged wheel running actograms from WT and Mc3r−/− mice showing baseline activity and response to a 5 h phase advance. The yellow and black sections indicate the lights-on and lights-off periods, respectively. Mean wheel running activity is shown for WT (+/+, n = 18) and Mc3r-deficient (−/−, n = 20) mice using a gray scale, with white representing no or minimal activity, and black representing peaks in activity. B, Averaged ratio of wheel running activity for each hour of the phase advance adjusted for normal activity (average normal wheel running for the 5 h after lights off) over the three experimental days. Onset of wheel running was dependent on genotype and was statically significant (*) between Mc3r−/− compared with WT mice, on hour 1 of day 1 (p < 0.05), on hour 2 on day 3 (*p < 0.05), and on hour 4 on day 6 (p < 0.02). n = 18–20 per group. One-way ANOVA with Tukey's post hoc test was performed to detect significant differences in wheel running data.