Effects of damage to SCN neurons and efferent pathways on circadian activity rhythms of hamsters

Harrington, Mary E.; Rahmani, Tayebeh; Lee, C.Allison

doi:10.1016/0361-9230(93)90097-u

Cited by 27 publications

(17 citation statements)

References 16 publications

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“…Relatively few SC N neurons may be required for circadian rhythms to persist (Davis and Gorski, 1984;Harrington et al, 1993); therefore the SCN lesions were made large to ensure that all SCN neurons were removed. However, it is unlikely that a pacemaker mediating treadmill entrainment resides among non-SCN nuclei that were also damaged because, as demonstrated next, entrainment required innervation of the SCN by NPY, and the NPY source neurons in the IGL do not innervate other nuclei in the vicinity of the SCN.…”

Section: Entrainment: Scn-ablated Micementioning

confidence: 99%

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: Entrainment: Scn-ablated Micementioning

confidence: 99%

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

1997

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“…In view of this complex topographical and functional organization, it is interesting to note that the SCN has historically been considered to be a functionally homogenous structure. For example, lesion studies suggest that survival of only a small fraction (ϳ25%) of any portion of the SCN is sufficient to support rhythmic function (Rusak, 1977;Van den Pol and Powley, 1979;Davis and Gorski, 1988;Harrington et al, 1993;Welsh et al, 1995). More recent work on clock gene expression and electrical activity in neurochemically defined SCN subregions suggest that the SCN is not functionally homogenous but instead that different subregions serve different functions (Hamada et al, 2001;Nakamura et al, 2001;Jobst and Allen, 2002).…”

Section: Introductionmentioning

confidence: 99%

Targeted Microlesions Reveal Novel Organization of the Hamster Suprachiasmatic Nucleus

Kriegsfeld¹,

LeSauter²,

Silver³

2004

J. Neurosci.

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“…It was initially reported that SCN-lesioned animals continued to be rhythmic so long as at least 20% of the nucleus remained intact (Davis and Gorski, 1988;Harrington et al, 1993;Rusak, 1977), suggesting that the SCN was a homogenous group of cells and that only a small number of these cells were required to maintain rhythmicity. It is well known that the SCN is structurally heterogeneous and can be subdivided into 2 portions, the ventrolateral or "core" and the dorsomedial or "shell" (Moore, 1996).…”

mentioning

confidence: 99%

Gates and Oscillators: A Network Model of the Brain Clock

et al. 2003

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The suprachiasmatic nuclei (SCN) control circadian oscillations of physiology and behavior. Measurements of electrical activity and of gene expression indicate that these heterogeneous structures are composed of both rhythmic and nonrhythmic cells. A fundamental question with regard to the organization of the circadian system is how the SCN achieve a coherent output while their constituent independent cellular oscillators express a wide range of periods. Previously, the consensus output of individual oscillators had been attributed to coupling among cells. The authors propose a model that incorporates nonrhythmic "gate" cells and rhythmic oscillator cells with a wide range of periods, that neither requires nor excludes a role for interoscillator coupling. The gate provides daily input to oscillator cells and is in turn regulated (directly or indirectly) by the oscillator cells. In the authors' model, individual oscillators with initial random phases are able to self-assemble so as to maintain cohesive rhythmic output. In this view, SCN circuits are important for self-sustained oscillation, and their network properties distinguish these nuclei from other tissues that rhythmically express clock genes. The model explains how individual SCN cells oscillate independently and yet work together to produce a coherent rhythm.

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Effects of damage to SCN neurons and efferent pathways on circadian activity rhythms of hamsters

Cited by 27 publications

References 16 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

Targeted Microlesions Reveal Novel Organization of the Hamster Suprachiasmatic Nucleus

Gates and Oscillators: A Network Model of the Brain Clock

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