Phase-dependent induction by light of rat Clock gene expression in the suprachiasmatic nucleus.
To clarify the role of Clock in the photic signal transduction of rat circadian clock, we cloned and sequenced rat Clock and examined the effect of a single light pulse on the Clock mRNA expression in the suprachiasmatic nucleus (SCN) by in situ hybridization. Rats were exposed to a 30 min light pulse ( approximately 300 lx) at one of six circadian phases in constant darkness (DD), and sacrificed 60 min after the light on. In the rats without light exposure, the mRNA level in the SCN was high at ZT (Zeitgeber time) 6 and low at ZT 18 and 22. Light exposure increased Clock mRNA level in the SCN in phase dependent manner. The mRNA level was significantly increased during the subjective night (ZT10-22). The light had no effect on the mRNA level during the subjective day (ZT2 and 6). The Clock mRNA was also detected in the piriform cortex (PC), and increased by light at ZT14. These results suggest that Clock transcription in the SCN is involved in the photic signal transduction of circadian clock in rats.
Abe
H
H
Department of Physiology, Hokkaido University School of Medicine, Sapporo 060-8638, Japan. hiroabe@med.hokudai.ac.jp
Honma
S
S
Namihira
M
M
Tanahashi
Y
Y
Ikeda
M
M
Yu
W
W
Honma
K
K
D056930:ARNTL Transcription Factors; D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins; D056926:CLOCK Proteins; D002940:Circadian Rhythm / Q000235:genetics*; D003001:Cloning, Molecular; D015342:DNA Probes; D018076:DNA, Complementary; D015870:Gene Expression / Q000502:physiology; D018257:Helix-Loop-Helix Motifs / Q000235:genetics; D017403:In Situ Hybridization; D008029:Lighting; D008297:Male; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017208:Rats, Wistar; D017386:Sequence Homology, Amino Acid; D013493:Suprachiasmatic Nucleus / Q000737:chemistry* / Q000502:physiology*; D015534:Trans-Activators / Q000235:genetics*; D014157:Transcription Factors / Q000235:genetics
D056930:ARNTL Transcription Factors; D051792:Basic Helix-Loop-Helix Proteins; D056926:CLOCK Proteins; D015342:DNA Probes; D018076:DNA, Complementary; D012333:RNA, Messenger; D015534:Trans-Activators; D014157:Transcription Factors; C538945:Clock protein, rat