Serotonergic afferents mediate activity-dependent entrainment of the mouse circadian clock
D. M. Edgar, M. S. Reid and W. C. Dement Department of Psychiatry and Behavioral Sciences, Stanford University School of Medicine, California 94305, USA. The circadian pacemaker located in the suprachiasmatic nuclei (SCN) of the hypothalamus receives serotonergic afferents from the midbrain raphe nu...
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Published in: | American journal of physiology. Regulatory, integrative and comparative physiology integrative and comparative physiology, 1997-07, Vol.273 (1), p.265-R269 |
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Main Authors: | , , |
Format: | Article |
Language: | eng |
Online Access: | Get full text |
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Summary: | D. M. Edgar, M. S. Reid and W. C. Dement
Department of Psychiatry and Behavioral Sciences, Stanford University School of Medicine, California 94305, USA.
The circadian pacemaker located in the suprachiasmatic nuclei (SCN) of the
hypothalamus receives serotonergic afferents from the midbrain raphe
nuclei, but the functional role of this projection is unclear. In rodents,
locomotor activity increases serotonin content in the SCN, and serotonergic
agonists phase shift the circadian clock in a manner closely similar to
voluntary bouts of vigorous exercise, suggesting that serotonergic
afferents could be part of the activity-dependent entrainment mechanism. We
investigated this possibility by selectively lesioning serotonin terminals
within and adjacent to the SCN by local microinjection of
5,7-dihydroxytryptamine in mice pretreated with desipramine. This treatment
decreased serotonin content 96 +/- 1% and 5-hydroxyindole-3-acetic acid
content below levels of detection (nearly 100%) but did not decrease
norepinephrine content or neuropeptide Y immunoreactivity in the SCN. These
lesions did not alter subsequent running activity levels, yet rendered mice
unable to synchronize to a regularly scheduled 2-h wheel running paradigm
that entrained sham-lesioned controls. Serotonin afferents are thus
necessary for activity-dependent entrainment in the mouse. |
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ISSN: | 0363-6119 1522-1490 |