Photostimulation alters c-Fos expression in the dorsal raphe nucleus

Document Type

Article

Abstract

Retinal afferents to the dorsal raphe nucleus (DRN) have been described in a number of species, including Mongolian gerbils, but functional correlates of this optic pathway are unknown at present. To determine whether temporally modulated photostimulation can affect c-Fos expression in the gerbil DRN, quantitative analysis of c-Fos-immunoreactive (c-Fos-ir) neurons was conducted following 60-min exposure to pulsed (2 Hz) photostimulation at selected times over the 12:12 h light/dark cycle. For comparison, c-Fos expression was also analyzed in the subnuclei of the lateral geniculate complex and in the suprachiasmatic nucleus (SCN). In the DRN, a substantial reduction was observed in the number of c-Fos immunoreactive (c-Fos-ir) neurons during the light period and early dark period in photostimulated vs. control animals. Similar results were obtained in the intergeniculate leaflet (IGL) and ventral lateral geniculate (VLG). However, no significant changes were observed in the number of c-Fos-ir neurons in the dorsal lateral geniculate nucleus or suprachiasmatic nucleus (SCN) following photostimulation, except for an increase in the middle of the dark period. These findings indicate that photic stimulation can lead to a suppression or down-regulation of c-Fos expression in the DRN that is probably mediated via the direct retinal pathway to the DRN in this species. The similarity between c-Fos expression profiles in the DRN and IGL/VGL suggest that efferent projections from the DRN may modulate c-Fos expression to visual stimulation in these subnuclei of the lateral geniculate complex.

Medical Subject Headings

Animals; Circadian Rhythm (physiology, radiation effects); Down-Regulation; Geniculate Bodies (cytology, metabolism, radiation effects); Gerbillinae; Immediate-Early Proteins (metabolism, radiation effects); Immunohistochemistry; Light; Light Signal Transduction (physiology); Male; Neurons (metabolism, radiation effects); Photic Stimulation; Proto-Oncogene Proteins c-fos (metabolism, radiation effects); Raphe Nuclei (cytology, metabolism, radiation effects); Suprachiasmatic Nucleus (cytology, metabolism, radiation effects); Visual Pathways (cytology, metabolism, radiation effects)

Publication Date

1-21-2005

Publication Title

Brain research

ISSN

0006-8993

Volume

1031

Issue

2

First Page

245

Last Page

52

PubMed ID

15649450

Digital Object Identifier (DOI)

10.1016/j.brainres.2004.10.054

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