title: Effect of photic stimuli disturbing overt circadian rhythms on the dorsomedial and ventrolateral SCN rhythmicity.
abstract: To ascertain how photic stimuli disturbing overt circadian rhythms affect the endogenous rhythmicity of the suprachiasmatic nucleus (SCN), rats were subjected to constant light (LL) or to a 9-h light pulse encompassing midnight, and rhythms of abundance of the c-Fos-immunoreactive (c-Fos-ir) and the PER1-immunoreactive (PER1-ir) cells were studied during the first 1-2 cycles following release into LL or darkness (DD) within the whole SCN as well as in its ventrolateral (vl) and the dorsomedial (dm) part. LL seemingly abolished the c-Fos rhythm in the whole SCN, while the rhythm persisted in the vl- and dm-SCN. In the dm-SCN, the rhythm of c-Fos-ir was phase-delayed by about 4 h in LL, whereas the rhythm of PER1-ir was affected just slightly. In the vl-SCN, the rhythm of c-Fos photo-induction might be delayed by 5-6 h as compared with the reported rhythm [A. Sumova and H. Illnerova, Am. J. Physiol. 274 (1998) R857-R863], whereas the PER1 profile appeared to be out of phase with that in DD. After a 9-h light pulse encompassing midnight, the rhythm of PER1-ir in the dm-SCN changed just slightly, whereas the PER1 rhythm in the vl-SCN was abolished and there was just an indication of extension of elevated PER1-ir. Altogether, the data indicate that photic stimuli disturbing circadian rhythms affect more dramatically the vl- than the dm-SCN rhythmicity within the first cycles and that in the dm-SCN shifting of the c-Fos rhythm proceeds more rapidly than that of the Per1 rhythm.
authors.affiliation: Department of Neurohumoral Regulations, Institute of Physiology, Academy of Sciences of Czech Republic, Videnska 1083, 142 20 Prague 4, Czech Republic. sumova@biomed.cas.cz
authors.forename: Alena
authors.initials: A
authors.lastname: Sumová
authors.forename: Helena
authors.initials: H
authors.lastname: Illnerová
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D002452:Cell Count / Q000379:methods; D018797:Cell Cycle Proteins; D002940:Circadian Rhythm / Q000528:radiation effects*; D007150:Immunohistochemistry / Q000379:methods; D008297:Male; D009474:Neurons / Q000378:metabolism / Q000528:radiation effects; D009687:Nuclear Proteins / Q000378:metabolism; D056950:Period Circadian Proteins; D010507:Periodicity; D010775:Photic Stimulation; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D013493:Suprachiasmatic Nucleus / Q000166:cytology / Q000378:metabolism / Q000528:radiation effects*
chemical_list: D018797:Cell Cycle Proteins; D009687:Nuclear Proteins; C539024:Per1 protein, rat; D056950:Period Circadian Proteins; D016760:Proto-Oncogene Proteins c-fos