@article {Prolo404, author = {Laura M. Prolo and Joseph S. Takahashi and Erik D. Herzog}, title = {Circadian Rhythm Generation and Entrainment in Astrocytes}, volume = {25}, number = {2}, pages = {404--408}, year = {2005}, doi = {10.1523/JNEUROSCI.4133-04.2005}, publisher = {Society for Neuroscience}, abstract = {In mammals, the master circadian pacemaker is considered the suprachiasmatic nucleus (SCN) of the hypothalamus. The SCN consists of a heterogeneous population of neurons and relatively understudied glia. We investigated whether glia, like neurons, rhythmically express circadian genes. We generated pure cultures of cortical astrocytes from Period2::luciferase (Per2::luc) knock-in mice and Period1::luciferase (Per1::luc) transgenic rats and recorded bioluminescence as a real-time reporter of gene activity. We found that rat Per1::luc and mouse Per2::luc astroglia express circadian rhythms with a genetically determined period. These rhythms damped out after several days but were reinitiated by a variety of treatments, including a full volume exchange of the medium. If cultures were treated before damping out, the phase of Per1::luc rhythmicity was shifted, depending on the time of the pulse relative to the peak of Per1 expression. Glial rhythms entrained to daily 1.5{\textdegree}C temperature cycles and were significantly sustained when cocultured with explants of the adult SCN but not with cortical explants. Thus, multiple signals, including a diffusible factor(s) from the SCN, are sufficient to either entrain or restart circadian oscillations in cortical glia.}, issn = {0270-6474}, URL = {https://www.jneurosci.org/content/25/2/404}, eprint = {https://www.jneurosci.org/content/25/2/404.full.pdf}, journal = {Journal of Neuroscience} }