Fig. 4.

Effect of long-term hypercholesterolemia on behavioral rhythms under constant darkness and group-housing conditions.

(A to D) Long-term monitoring of locomotor activity was performed over a period of up to about 160 days in constant darkness. Two representative raw activity data of wild-type mice and Ldlr −/− mice (+ HFD) and are shown in (A) and (C), respectively. A few individuals became desynchronized from other animals. The five-day free-running period and amplitude of circadian behavioral rhythms were calculated with a chi-square periodogram at intervals of about 40 days. The data indicate a representative of four wild-type groups (B) and eight Ldlr −/− (+ HFD) groups (D). 12-h rhythms (red asterisks) were detectable at days 40–44, 80–84 and 120–124, although only 24-h rhythms (black asterisks) were detectable at days 2–6. The numbers shown under the periodograms indicate the average ± SE of 24-h/12-h period and amplitude (n = 4 or 8 groups).