Serotonergic stimulation and nonphotic phase-shifting in hamsters

Stimuli that make hamsters active, such as dark pulses or triazolam administration, also phase shift their circadian clocks, producing phase advances during the subjective day and phase delays during the subjective night. Activity or its correlate appears to be important in producing the shifts beca...

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Bibliographic Details
Published in:Physiology & behavior 1996-02, Vol.59 (2), p.221-230
Main Authors: Bobrzynska, Kasia J., Godfrey, Matthew H., Mrosovsky, N.
Format: Article
Language:English
Subjects:
8-Hydroxy-2-(di-n-propylamino)tetralin - pharmacology
Activity
Animals
Arousal - drug effects
Arousal - physiology
Biological and medical sciences
Chronobiology
Circadian
Circadian Rhythm - drug effects
Circadian Rhythm - physiology
Cricetinae
Fundamental and applied biological sciences. Psychology
Hamster
Light
Male
Mesocricetus
Motor Activity - drug effects
Motor Activity - physiology
Nonphotic
Phase shift
Receptors, Serotonin - drug effects
Receptors, Serotonin - physiology
Serotonin
Serotonin - physiology
Serotonin Receptor Agonists - pharmacology
Sleep - drug effects
Sleep - physiology
Vertebrates: anatomy and physiology, studies on body, several organs or systems
Wakefulness - drug effects
Wakefulness - physiology
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Summary:Stimuli that make hamsters active, such as dark pulses or triazolam administration, also phase shift their circadian clocks, producing phase advances during the subjective day and phase delays during the subjective night. Activity or its correlate appears to be important in producing the shifts because preventing locomotion blocks the phase shifts associated with these stimuli. The physiological basis of clock resetting induced by activity is not fully understood. The serotonergic (5-HT) projection from the raphe to the suprachiasmatic nucleus (SCN) is a possible route by which nonphotic information could reach the pacemaker. Administration of 8-HYDROXY-2-(DI- N-PROPYLAMINO) TETRALIN HYDROBROMIDE (8-OH-DPAT), a 5-HT 1A and 5-HT7 receptor agonist, at circadian time (CT) 8 produces phase advances in the circadian rhythms of hamsters. Before concluding that 5-HT mediates the effect of activity on the pacemaker, it must be shown that 5-HT agonists do not produce shifts simply because they make animals more active. Therefore, we investigated the contribution of activity to 8-OH-DPAT-produced shifts. Preventing hamsters from moving around after administering 8-OH-DPAT did not abolish phase shifts. Moreover, higher doses of 8-OH-DPAT diminished activity on the day of injection but did not affect the amplitude of phase shifts. Surprisingly, quipazine (a non specific 5-HT agonist), when injected in the middle of subjective day did not phase shift the activity rhythm of hamsters, as it has been reported to do in rats.
ISSN:0031-9384
1873-507X
DOI:10.1016/0031-9384(95)02130-2