@article {Coogan3085, author = {Andrew N. Coogan and Hugh D. Piggins}, title = {Circadian and Photic Regulation of Phosphorylation of ERK1/2 and Elk-1 in the Suprachiasmatic Nuclei of the Syrian Hamster}, volume = {23}, number = {7}, pages = {3085--3093}, year = {2003}, doi = {10.1523/JNEUROSCI.23-07-03085.2003}, publisher = {Society for Neuroscience}, abstract = {In this study we investigated the circadian and photic regulation of phosphorylation of the extracellular signal-related kinase (ERK) 1/2, and the transcription factor Elk-1 in the suprachiasmatic nuclei of the Syrian hamster. We report that levels of phosphorylated ERK (P-ERK) are rhythmic, peaking during the mid subjective day, whereas phosphorylated Elk-1 (P-Elk-1) shows no distinct rhythm. Light pulses during the subjective night rapidly, but transiently, induce P-ERK, whereas P-Elk-1 is also induced, albeit with a slower time course. Application of the ERK pathway inhibitor U0126 attenuates photic induction of both P-ERK and P-Elk-1 and phase advances of wheel-running behavior. The NMDA receptor channel blocker, MK-801, also significantly attenuates photic induction of P-ERK and P-Elk-1. Taken together, these results indicate a role of the ERK cascade in the regulation of free-running circadian rhythms and of photic-resetting of these rhythms and suggest that in the mammalian suprachiasmatic nuclei, Elk-1 represents a novel molecular component of the photic-induction pathway.}, issn = {0270-6474}, URL = {https://www.jneurosci.org/content/23/7/3085}, eprint = {https://www.jneurosci.org/content/23/7/3085.full.pdf}, journal = {Journal of Neuroscience} }