Structural and functional changes in the suprachiasmatic nucleus following chronic circadian rhythm perturbation

▶The responses of circadian system to long-term perturbation were examined in rats utilizing a weekly phase shifting paradigm. ▶The behavioral rhythms were approximately re-entrained by the end of each shift, and the rate of re-entrainment accelerated following multiple shifts. ▶The SCN sub-regions resynchronized with each other by day 7 following the 4th phase advance. ▶The output control of the SCN was attenuated following four weekly phase advances. ▶The responses of the SCN depend upon the direction and duration of the phase shifts.