Ontogeny of photic-induced c-fos mRNA expression in rat suprachiasmatic nuclei

ArticleinNeuroreport 5(18):2683-7 · January 1995with3 Reads
Impact Factor: 1.52 · DOI: 10.1097/00001756-199412000-00069 · Source: PubMed


    The suprachiasmatic nucleus (SCN) of the hypothalamus contains a circadian pacemaker that controls a variety of physiological and behavioral rhythms. Photic induction of immediate early genes such as c-fos in the SCN occurs in a circadian-phase dependent manner, suggesting that c-fos may be part of the pathway for entrainment of circadian rhythms. The purpose of this study was to determine the point in development when photic stimuli can first activate c-fos mRNA expression in the rat SCN. The results indicate that photic stimulation can induce statistically significant c-fos mRNA expression at circadian time 22 (CT22) on postnatal day 1 (P1), although hybridization above background levels can be detected in the SCN of some rat pups earlier in the subjective night. We infer that a multi-step pathway between visual transduction by the retina and regulation of c-fos transcription in SCN cells must be mature by CT22 on P1.