Journal
JOURNAL OF NEUROSCIENCE
Volume 25, Issue 40, Pages 9304-9308Publisher
SOC NEUROSCIENCE
DOI: 10.1523/jneurosci.2733-05.2005
Keywords
clock; rhythm; SCN2.2; Per2; Bmal1; cadmium
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Funding
- NINDS NIH HHS [P01 NS39546, P01 NS039546] Funding Source: Medline
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Individual neurons within the suprachiasmatic nuclei (SCNs) are capable of functioning as autonomous clocks and generating circadian rhythms in the expression of genes that form the molecular clockworks. Limited information is available on how these molecular oscillations in individual clock cells are coordinated to provide for the ensemble rhythmicity that is normally observed from the entire SCN. Because calcium influx via voltage-dependent calcium channels (VDCCs) has been implicated in the regulation of gene expression and synchronization of rhythmicity across the population of SCN clock cells, we first examined the rat SCN and an immortalized line of SCN cells (SCN2.2) for expression and circadian regulation of different VDCC alpha 1 subunits. The rat SCN and SCN2.2 cells exhibited mRNA expression for all major types of VDCC alpha 1 subunits. Relative levels of VDCC expression in the rat SCN and SCN2.2 cells were greatest for L-type channels, moderate for P/Q-and T-type channels, and minimal for R- and N-type channels. Interestingly, both rat SCN and SCN2.2 cells showed rhythmic expression of P/Q- and T-type channels. VDCC involvement in the regulation of molecular rhythmicity in SCN2.2 cells was then examined using the nonselective antagonist, cadmium. The oscillatory patterns of rPer2 and rBmal1 expression were abolished in cadmium-treated SCN2.2 cells without affecting cellular morphology and viability. These findings raise the possibility that the circadian regulation of VDCC activity may play an important role in maintaining rhythmic clock gene expression across an ensemble of SCN oscillators.
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