Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.06.05.136440v1?rss=1 Authors: Kim, S., McMahon, D. G. Abstract: Entrainment of the suprachiasmatic nucleus (SCN) circadian clock in the brain to environmental light cycles is a form of neural plasticity which involves acute daily clock resetting, and long-term changes in endogenous clock period. Elucidating mechanisms of entrainment is critical for understanding how circadian clocks maintain alignment of internal rhythms with the external environment. However, studying how the SCN clock per se behaves throughout entrainment at the molecular level remains technically challenging. Here we report a novel experimental system that precisely employs periodic optogenetic stimulation to drive circadian entrainment of multiple SCN brain slices while recording circadian rhythms in molecular output with bioluminescence. Using this system, we demonstrate entrainment of the SCN clock ex vivo and show that many forms of circadian clock plasticity in behavior is intrinsic to the SCN molecular clock plasticity induced through encoding different light cycle periods and seasonal variations in the day length. Copy rights belong to original authors. Visit the link for more info