The hypothalamic suprachiasmatic nucleus (SCN) is the primary modulator of circadian rhythms in mammals. This central pacemaker endogenously generates near-24h oscillations and integrates varied environmental, neuronal and humoral signals to adjust the phase of circadian rhythms throughout an organism. Many of these input/output pathways have been thoroughly mapped utilizing a broad spectrum of experimental approaches. These include analysis of behavior, biochemistry, electrophysiology and more recently, real-time in vivo reporting systems. However, many of these systems, while integral to mammalian circadian research, are laborious and relatively low-throughput. Nevertheless, the more recent discovery of peripheral circadian oscillators has uncovered an opportunity to utilize cellular systems that provide an additional perspective of molecular clock mechanism. In these studies, a high-throughput cellular circadian system in Rat-1 fibroblasts (see Hurst et al., 2003 SFN abstract) was employed to determine ...