Resilience of Circadian Pacemaker Development in Hamsters

Disruptions of circadian rhythms have been linked to a wide range of pathologies from sleep disorders to cancer. The extent to which disruptions of circadian rhythms during development contribute to later conditions is not known. The present study tested the hypothesis that functional properties of the central circadian pacemaker, the suprachiasmatic nucleus (SCN), are affected by abnormal entrainment during development. The SCN is specialized for the generation of robust rhythms, for direct and indirect output to physiological and behavioral systems, and for entrainment to light/dark cycles via direct retinal input. It consists of thousands of neurons and glia with distinct phenotypes and has subdivisions delineated by both anatomical and functional criteria. In rodents, SCN rhythms develop within days after SCN cells are produced and before many other aspects of differentiation, such as synaptogenesis, are complete. We demonstrated that around the time of birth, the hamster SCN in vivo can undergo repea...