Nonphotic entrainment by 5-HT1A/7 receptor agonists accompanied by reduced Per1 and Per2 mRNA levels in the suprachiasmatic nuclei.
In mammals, the environmental light/dark cycle strongly synchronizes the circadian clock within the suprachiasmatic nuclei (SCN) to 24 hr. It is well known that not only photic but also nonphotic stimuli can entrain the SCN clock. Actually, many studies have shown that a daytime injection of 8-hydroxy-2-(di-n-propylamino) tetralin (8-OH DPAT), a serotonin 1A/7 receptor agonist, as a nonphotic stimulus induces phase advances in hamster behavioral circadian rhythms in vivo, as well as the neuron activity rhythm of the SCN in vitro. Recent reports suggest that mammalian homologs of the Drosophila clock gene, Period (Per), are involved in photic entrainment. Therefore, we examined whether phase advances elicited by 8-OH DPAT were associated with a change of Period mRNA levels in the SCN. In this experiment, we cloned partial cDNAs encoding hamster Per1, Per2, and Per3 and observed both circadian oscillation and the light responsiveness of Period. Furthermore, we found that the inhibitory effect of 8-OH DPAT on hamster Per1 and Per2 mRNA levels in the SCN occurred only during the hamster's mid-subjective day, but not during the early subjective day or subjective night. The present findings demonstrate that the acute and circadian time-dependent reduction of Per1 and/or Per2 mRNA in the hamster SCN by 8-OH DPAT is strongly correlated with the phase resetting in response to 8-OH DPAT.
Horikawa
K
K
Department of Pharmacology and Brain Science and Advanced Research Center for Human Sciences, School of Human Sciences, Waseda University, Tokorozawa, Saitama, Japan.
Yokota
S
S
Fuji
K
K
Akiyama
M
M
Moriya
T
T
Okamura
H
H
Shibata
S
S
D017371:8-Hydroxy-2-(di-n-propylamino)tetralin / Q000494:pharmacology; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects / Q000502:physiology; D018797:Cell Cycle Proteins; D002940:Circadian Rhythm / Q000502:physiology*; D006224:Cricetinae; D015870:Gene Expression / Q000187:drug effects / Q000502:physiology; D008297:Male; D008647:Mesocricetus; D009043:Motor Activity / Q000187:drug effects / Q000502:physiology; D009687:Nuclear Proteins / Q000235:genetics*; D056950:Period Circadian Proteins; D010775:Photic Stimulation; D012333:RNA, Messenger / Q000378:metabolism; D011985:Receptors, Serotonin / Q000502:physiology*; D044263:Receptors, Serotonin, 5-HT1; D017366:Serotonin Receptor Agonists / Q000494:pharmacology; D013493:Suprachiasmatic Nucleus / Q000502:physiology*; D014157:Transcription Factors
D018797:Cell Cycle Proteins; D009687:Nuclear Proteins; C513312:Per2 protein, mouse; D056950:Period Circadian Proteins; D012333:RNA, Messenger; D011985:Receptors, Serotonin; D044263:Receptors, Serotonin, 5-HT1; D017366:Serotonin Receptor Agonists; D014157:Transcription Factors; D017371:8-Hydroxy-2-(di-n-propylamino)tetralin