Figure 5.

Scheme of circadian hepatocyte clock synchrony in control animals and in absence of the SCN or other extrahepatic clocks. (A) In intact, behaviorally rhythmic mice, the central pacemaker in the SCN synchronizes circadian oscillators to similar phases in peripheral organs (red arrow). The phases of peripheral clocks are somewhat delayed with regard to the phase of the SCN (Damiola et al. 2000). (B) In SCN-lesioned, behaviorally arrhythmic mice, the circadian clocks of different peripheral organs have different phases, but within the liver the cellular oscillators remain synchronized. (C) In behaviorally arrhythmic “hepatocyte clock-only mice,” a large proportion of hepatocyte clocks are still in phase. The findings illustrated in B and C suggest that circadian hepatocyte oscillators are phase coupled, as indicated by the yellow lines connecting hepatocyte clocks.