Reorganization of the suprachiasmatic nucleus coding for day length.
In mammals, the suprachiasmatic nucleus (SCN), the circadian pacemaker, receives light information via the retina and functions in the entrainment of circadian rhythms and in phasing the seasonal responses of behavioral and physiological functions. To better understand photoperiod-related alterations in the SCN physiology, we analyzed the clock gene expression in the mouse SCN by performing in situ hybridization and real-time monitoring of the mPer1::luc bioluminescence. Under long photoperiod (LP) conditions, the expression rhythms of mPer1 and Bmal1 in the caudal SCN phase-led those in the rostral SCN; further, within the middle SCN, the rhythms in the ventrolateral (VL)-like subdivision advanced compared with those in the dorsomedial (DM)-like subdivision. The mPer1::luc rhythms in the entire coronal slice obtained from the middle SCN exhibited 2 peaks with a wide peak width under LP conditions. Imaging analysis of the mPer1::luc rhythms in several subdivisions of the rostral, middle, caudal, and horizontal SCN revealed wide regional variations in the peak time in the rostral half of the SCN under LP conditions. These variations were not due to alterations in the waveform of a single SCN neuronal rhythm. Our results indicate that LP conditions induce phase changes in the rhythms in multiple regions in the rostral half of the SCN; this leads to different circadian waveforms in the entire SCN, coding for day length.
Naito
Emiko
E
Division of Biomodeling, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Japan.
Watanabe
Tsuyoshi
T
Tei
Hajime
H
Yoshimura
Takashi
T
Ebihara
Shizufumi
S
D056930:ARNTL Transcription Factors; D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics / Q000378:metabolism; D001683:Biological Clocks / Q000502:physiology; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D002940:Circadian Rhythm / Q000502:physiology*; D017403:In Situ Hybridization; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D009043:Motor Activity / Q000502:physiology; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D056950:Period Circadian Proteins; D017440:Photoperiod; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D013493:Suprachiasmatic Nucleus / Q000166:cytology / Q000502:physiology
D056930:ARNTL Transcription Factors; D051792:Basic Helix-Loop-Helix Proteins; D018797:Cell Cycle Proteins; D009687:Nuclear Proteins; D056950:Period Circadian Proteins; D011993:Recombinant Fusion Proteins; C538961:Bmal1 protein, mouse; C539023:Per1 protein, mouse