Participation of transcription factors from the Rel/NF-kappa B family in the circadian system in hamsters.

We have studied the presence and activity of components of the nuclear factor-kappaB (NF-kappaB) transcription factor in the hamster circadian system analyzing wheel-running activity, protein expression and DNA binding activity by electrophoresis mobility shift assays (EMSA). Non-rhythmic specific immunoreactive bands corresponding to a NF-kappaB subunit (p65) were found in hamster suprachiasmatic nuclei (SCN) homogenates. The active form of NF-kappaB evidenced by EMSA was clear and specific in SCN nuclear extracts. The administration of the NF-kappaB inhibitor pyrrolidine-dithiocharbamate (PDTC) blocked the light-induced phase advance at circadian time 18 (vehicle+light pulse: 2.08+/-0.46 h, PDTC+light: 0.36+/-0.35 h). These results demonstrate the presence and activity of Rel/NF-kappaB family proteins in the hamster SCN and suggest that these proteins may be related to the entrainment and regulation of circadian rhythms.