RHYTHMSSerotonin depletion decreases light induced c-fos in the rat suprachiasmatic nucleusMoyer, Robert W.1,2; Kennaway, David J.1Author Information 1Department of Obstetrics and Gynaecology, The University of Adelaide Medical School, Frome Rd, Adelaide, SA 5005, Australia 2Corresponding Author: Robert W. Moyer Acknowledgements: This research was supported by a National Health and Medical Research Council Grant to D.J.K. The authors wish to thank Dr S.A. Ferguson for critically reading the manuscript. Received 22 December 1999; accepted 25 January 2000 NeuroReport: April 7, 2000 - Volume 11 - Issue 5 - p 1021-1024 Buy Abstract The suprachiasmatic nucleus (SCN) is the locus of the biological clock in mammals. Daily light cycles entrain the endogenous circadian rhythms in mammals through direct and indirect neural pathways from the retinae to the suprachiasmatic nucleus. We have studied the effect of serotonin depletion on the photic induction of the early response gene c- fos in the SCN of rats. Serotonin depletion, verified by immunohistochemistry, produced a significant decrease (42%) in the number of c-FOS positive cells in the ventrolateral portion of the SCN. These results support the involvement of serotonin as a mediator of photic information to the SCN through the retinal projection to the dorsal raphe nucleus. © 2000 Lippincott Williams & Wilkins, Inc.