Photic and circadian regulation of c-fos gene expression in the hamster suprachiasmatic nucleus

Jon M. Kornhauser, Dwight E. Nelson, Kelly E. Mayo, Joseph S. Takahashi

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Abstract

Photic information entrains a circadian pacemaker located in the suprachiasmatic nucleus (SCN) of the mammalian hypothalamus to environmental light/dark cycles. To determine whether light regulates c-fos gene expression in the SCN, we have measured c-fos mRNA levels in the SCN of the golden hamster. We report that, during the subjective night, light causes a rapid increase in levels of c-fos mRNA in the SCN. Light pulses of 5 min duration are sufficient to induce c-fos mRNA, and the highest mRNA levels occur 30 min following the onset of light. The minimum level of illumination required to induce an increase in c-fos mRNA is indistinguishable from the minimum irradiance that produces a phase shift in the hamster's circadian rhythm of activity. In addition, the induction of c-fos mRNA in the SCN by light is itself under circadian regulation. Light induction of c-fos mRNA occurs only during the subjective night, at circadian times when photic phase shifting of activity occurs. Taken together, these data suggest that c-fos may be a molecular component of the photic pathway for entrainment of mammalian circadian rhythms.

Original languageEnglish (US)
Pages (from-to)127-134
Number of pages8
JournalNeuron
Volume5
Issue number2
DOIs
StatePublished - Aug 1990

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ASJC Scopus subject areas

  • Neuroscience(all)

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