Ontogeny of photic-induced c-fos mRNA expression in rat suprachiasmatic nuclei.
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.
Leard
L E
LE
Department of Biological Sciences, Stanford University, CA 94305-5020.
Macdonald
E S
ES
Heller
H C
HC
Kilduff
T S
TS
D000375:Aging / Q000502:physiology; D000818:Animals; D000831:Animals, Newborn / Q000254:growth & development*; D001345:Autoradiography; D016762:Genes, fos / Q000528:radiation effects*; D006651:Histocytochemistry; D017403:In Situ Hybridization; D008027:Light; D012333:RNA, Messenger / Q000378:metabolism*; D051381:Rats / Q000502:physiology*; D017207:Rats, Sprague-Dawley; D013493:Suprachiasmatic Nucleus / Q000378:metabolism*
D012333:RNA, Messenger