%0 Journal Article %A Laura M. Prolo %A Joseph S. Takahashi %A Erik D. Herzog %T Circadian Rhythm Generation and Entrainment in Astrocytes %D 2005 %R 10.1523/JNEUROSCI.4133-04.2005 %J The Journal of Neuroscience %P 404-408 %V 25 %N 2 %X 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°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. %U https://www.jneurosci.org/content/jneuro/25/2/404.full.pdf