A serotonin neurotoxin attenuates the phase-shifting effects of triazolam on the circadian clock in hamsters

Penev, Plamen D.; Turek, Fred W.; Zee, Phyllis C.

doi:10.1016/0006-8993(94)01237-c

Cited by 38 publications

(22 citation statements)

References 51 publications

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“…Third, there are two reports that depletion of SC N 5-HT in Syrian hamsters by 5,7-DHT does not prevent phase shifts to activity-inducing stimuli (Meyer and Morin, 1995;Bobrzynska et al, 1996b). In addition, 5-HT lesions that did attenuate nonphotic resetting in hamsters also attenuated (Cutrera et al, 1994) or may have attenuated (Penev et al, 1995) the primary activity bout that served as the resetting stimulus. Finally, 5-HT antagonists with affinity for 5-HT 7 receptors, the most likely to mediate 5-HT-induced phase resetting of the SC N pacemaker (L ovenberg et al, 1993), do not attenuate activity-induced shifts in hamsters (Antle et al, 1997).…”

Section: Mixed Evidence That 5-ht Mediates Entrainment By Activitymentioning

confidence: 98%

“…Raphe nuclei unit activity and SCN 5-HT levels correlate positively with motor activity (Shioiri et al, 1991;Jacobs and Azmitia, 1992;Dudley and Glass, 1996), 5-HT agonists can produce phase shifts of behavioral rhythms or SCN rhythms in vitro that are approximately similar in timing, if not magnitude, to those induced by scheduled running (Prosser et al, 1990;Tominaga et al, 1992;Edgar et al, 1993;Bobrzynska et al, 1996a), and the 5-HT antagonists ritanserin and ketanserin can attenuate the small phase shifts caused by arousing saline injections in hamsters (Sumova et al, 1996). Reduction of hypothalamic 5-HT by 5,7-DHT (Cutrera et al, 1994) or p-chloroamphetamine (Penev et al, 1995) has been reported to block the phase-shifting effects of triazolam-induced running. Finally, SCN 5-HT denervation by 5,7-DHT can prevent entrainment to scheduled yet voluntary home cage wheel activity in mice (Edgar et al, 1997).…”

Section: Mixed Evidence That 5-ht Mediates Entrainment By Activitymentioning

confidence: 99%

“…This confound is particularly problematic for interpreting the role of NPY in mice, given that studies using other methods have not yet been done in this species. Similarly, reduced activity cannot be ruled out as the explanation for attenuation of nonphotic shifting in hamsters after neurochemical depletion of serotonin (5-HT) (Cutrera et al, 1994;Penev et al, 1995).…”

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confidence: 99%

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Both Neuropeptide Y and Serotonin Are Necessary for Entrainment of Circadian Rhythms in Mice by Daily Treadmill Running Schedules

1997

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This study investigated the role of the suprachiasmatic nucleus (SCN) circadian pacemaker and its neuropeptide Y (NPY) and serotonin (5-HT) afferents in entrainment (synchronization) of mouse circadian rhythms by treadmill running. Blind C57BL/6j mice were run in treadmills for 3 hr/d for 3-10 weeks after receiving radio-frequency lesions of the SCN or the intergeniculate leaflet (IGL, the source of SCN NPY) or infusions of the 5-HT neurotoxin 5,7-DHT into the SCN area. Of 25 intact mice, 22 entrained and three showed period (, the mean duration of the circadian cycle) modulations to scheduled running. Arrhythmic SCN-ablated mice did not synchronize to scheduled running in a way suggestive of circadian pacemaker mediation. Of 15 mice with IGL lesions, only two with partial lesions entrained. Mice with complete IGL lesions (five), confirmed by immunocytochemistry, showed no entrainment or changes. Of 19 mice with 5-HT lesions, only two with partial lesions entrained. All but two mice with complete (10) or nearly complete (4) 5-HT denervation, confirmed by immunocytochemistry, showed modulations during the treadmill schedule. Failure to entrain was not explained by group differences in before the treadmill schedules. The results indicate that the SCN and both NPY and 5-HT are necessary for entrainment to 24 hr schedules of forced running but that complete loss of 5-HT does not prevent modulations of pacemaker motion by behavioral stimuli. Treadmill entrainment in mice may involve synergistic interactions between 5-HT and NPY afferents at some site within the circadian system.

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Section: Mixed Evidence That 5-ht Mediates Entrainment By Activitymentioning

confidence: 98%

Section: Mixed Evidence That 5-ht Mediates Entrainment By Activitymentioning

confidence: 99%

mentioning

confidence: 99%

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Both Neuropeptide Y and Serotonin Are Necessary for Entrainment of Circadian Rhythms in Mice by Daily Treadmill Running Schedules

1997

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“…Furthermore, lesions of the IGL block many nonphotic phase shifts [136,138] . Serotonin-containing cells of the median raphe nucleus of the midbrain, which project to the SCN as well as to other brain regions, are also necessary for nonphotic phase shifts induced by triazolam injections [142][143][144] . Circadian information generated by the SCN pacemaker is transmitted to multiple targets in the hypothalamus, thalamus and limbic system, by efferent projections arising from both the dorsal and ventral SCN regions (see fig.…”

Section: Basic Anatomy and Physiology Of The Circadian Timing Systemmentioning

confidence: 99%

“…In addition to the geniculohypothalamic tract, serotonergic fibers from the midbrain median raphe nucleus project to the SCN and this projection is necessary for the occurrence of nonphotic phase shifts that are induced by triazolam [142][143][144] . Although aging has been reported to lead to degenerative changes in serotonin terminals in many rat brain regions, this effect has not been shown to occur in the SCN [195,196] .…”

Section: Effects Of Aging On Input Pathways To the Scn Master Circadimentioning

confidence: 99%

Aging of the Mammalian Circadian Timing System: Changes in the Central Pacemaker and Its Regulation by Photic and Nonphotic Signals

Duncan¹

2006

Neuroembryol Aging

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Aging alters many aspects of endogenously regulated, 24-hour (circadian) rhythms, such as their amplitude, relationship to the ambient lighting cycle, and sensitivity to phase resetting signals. In order to elucidate the mechanisms responsible for these age-related changes, many studies have investigated age-related changes in the neural components of the circadian timing system, which include the hypothalamic suprachiasmatic nucleus (SCN), the site of the mammalian master circadian pacemaker, its afferent projections from the retina, thalamus, and midbrain raphe, and its efferent projections to the hypothalamus, thalamus and limbic system. Studies have shown that the SCN exhibits age-related changes in electrical activity rhythms in the absence of neurodegeneration. Also, aging selectively decreases SCN expression of the circadian clock genes, Clock and Bmal1, as well as vasoactive intestinal peptide. The latter participates in mediating light-induced phase resetting of the circadian pacemaker and the amplitude of the preovulatory luteinizing hormone surge, which are both attenuated by aging. Furthermore, by decreasing serotonin 5-HT₇ receptors in the dorsal raphe, aging reduces one type of nonphotic input to the SCN. This review describes which aspects of circadian rhythm regulation exhibit changes during aging, as well as which mechanisms appear to be spared or remain to be explored.

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Function and Pharmacology of Circadian Clocks

Lundkvist

Block

2007

Handbook of Contemporary Neuropharmacology

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Biological timing systems are complex structures in higher organisms, generating biological and physiological functions with a periodicity of approximately 24 h. Knowledge of the structure and function of biological clocks has emerged from research on both invertebrate and vertebrate models. In humans, the master clock is located in the hypothalamus in the brain. Daily rhythms such as the sleep–wake cycle and hormonal rhythms can be modulated and disturbed by a number of pharmacological compounds. Drug therapy can be administered in a circadian fashion ( chronopharmacology ), thus taking into account the powerful circadian impact on drug toxicity and efficacy. This review will describe circadian systems and pharmacological impact on the timing structures.

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A serotonin neurotoxin attenuates the phase-shifting effects of triazolam on the circadian clock in hamsters

Cited by 38 publications

References 51 publications

Both Neuropeptide Y and Serotonin Are Necessary for Entrainment of Circadian Rhythms in Mice by Daily Treadmill Running Schedules

Both Neuropeptide Y and Serotonin Are Necessary for Entrainment of Circadian Rhythms in Mice by Daily Treadmill Running Schedules

Aging of the Mammalian Circadian Timing System: Changes in the Central Pacemaker and Its Regulation by Photic and Nonphotic Signals

Function and Pharmacology of Circadian Clocks

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