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Neuroreport. 1993 Oct 25;5(1):49-52.

Serotonin in the raphe nuclei: regulation by light and an endogenous pacemaker.

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Laboratory of Integrative Brain Function, Mitsubishi Kasei Institute of Life Sciences, Tokyo, Japan.


Temporal changes of serotonin (5-HT) content in the median (MRN) and dorsal (DRN) raphe nuclei were measured in rats kept under various lighting conditions. Serotonin content in the MRN and DRN under light-dark (LD) condition showed diurnal rhythmicity, with a peak during early light phase and a trough during the dark phase. In constant dark (DD) condition, a single peak was observed and was out of phase to the 5-HT peak found under LD condition. Animals exposed to constant light (LL) after 2 days in DD showed marked increase in 5-HT after lights on. These results suggest that changes in 5-HT in the MRN and DRN are regulated by an endogenous pacemaker and by light.

[Indexed for MEDLINE]

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