Circadian Rhythms of C‐FOS Expression in the Suprachiasmatic Nuclei of the Common Vole (Microtus arvalis)

In the common vole, rhythmic c-Fos expression in the dorsomedial SCN peaks during the light period under a 12:12 light/dark cycle.

• C-FOS expression in the dorsomedial SCN is rhythmic under light/dark conditions but becomes non-rhythmic under constant dim light.
• The pattern of C-FOS expression in voles may indicate a weak circadian organization of behavioral activity.
• In the ventrolateral SCN, C-FOS expression rises before lights-on and peaks at both lights-on and lights-off.
• The timing of peaks in ventrolateral C-FOS expression does not shift with changes in the light schedule, suggesting an internal process may regulate expression.

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