Effect of long-term exposure to constant dim light on the circadian system of rats.
The newly discovered multi-oscillatory nature of the mammalian circadian clock system and the cloning of the genes involved in the molecular mechanism that generates circadian rhythmicity have opened new approaches for understanding how mammals are temporally organized and how the mammalian circadian system reacts to the lack of normal synchronization cues. In the present study we investigated the effects of long-term exposure to constant red dim light on the pattern of the expression of Period 1 in the suprachiasmatic nuclei of the hypothalamus and of Arylalkylamine N-acetyltransferase(Aa-nat) in the retina and pineal gland. Our data demonstrate that Period 1 mRNA expression in the suprachiasmatic nuclei of the hypothalamus was not affected by exposure to constant red dim light for 60 days, whereas Aa-nat mRNA expression in the retina and in the pineal gland was significantly affected, since in some animals (20-30%) Aa-nat mRNA levels were found to be higher during the subjective day. A circadian rhythm of serum melatonin and locomotor activity was present in all the animals tested. In 4 animals serum melatonin levels were high during the subjective day. Our data suggest that long-term exposure to constant red dim light may induce desynchronization between the circadian rhythm of locomotor activity and serum melatonin levels.
Fukuhara
Chiaki
C
Neuroscience Institute and NSF Center for Behavioral Neuroscience, Morehouse School of Medicine, Atlanta, GA 30310, USA.
Aguzzi
Jacopo
J
Bullock
Nicole
N
Tosini
Gianluca
G
D000818:Animals; D047068:Arylalkylamine N-Acetyltransferase / Q000235:genetics / Q000378:metabolism; D018797:Cell Cycle Proteins; D002940:Circadian Rhythm / Q000528:radiation effects*; D005786:Gene Expression Regulation / Q000528:radiation effects*; D017403:In Situ Hybridization / Q000379:methods; D008027:Light; D008297:Male; D008550:Melatonin / Q000097:blood; D009043:Motor Activity / Q000502:physiology / Q000528:radiation effects; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D056950:Period Circadian Proteins; D010870:Pineal Gland / Q000528:radiation effects*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D012160:Retina / Q000528:radiation effects*; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D012701:Serotonin / Q000097:blood; D013493:Suprachiasmatic Nucleus / Q000528:radiation effects*; D013995:Time; D013997:Time Factors
D018797:Cell Cycle Proteins; D009687:Nuclear Proteins; C539022:PER1 protein, human; C539024:Per1 protein, rat; D056950:Period Circadian Proteins; D012333:RNA, Messenger; D012701:Serotonin; D047068:Arylalkylamine N-Acetyltransferase; D008550:Melatonin