Light-induced c-Fos expression in the mouse suprachiasmatic nucleus: immunoelectron microscopy reveals co-localization in multiple cell types.
Although light is known to regulate the level of c-fos gene expression in the suprachiasmatic nucleus (SCN), the site of an endogenous circadian clock, little is known about the identities of the photically activated cells. We used light-microscopic immunocytochemistry and immunoelectron microscopy to detect c-Fos protein in the SCN of Sabra mice exposed to brief nocturnal light pulses at zeitgeber time 15-16. Stimulation with light pulses that saturated the phase-shifting response of the circadian locomotor rhythm revealed an upper limit to the number of photo-inducible c-Fos cells at about one-fifth of the estimated total SCN cell population. This functionally defined set was morphologically and phenotypically heterogeneous. About 24% could be labelled for vasoactive intestinal polypeptide, 13% for vasopressin-neurophysin, and 7% for glial fibrillary acidic protein. The remaining 56% of c-Fos-positive cells were largely of unknown phenotype, although many were presumptive interneurons, some of which were immunoreactive for nitric oxide synthase.
Castel
M
M
Department of Cell and Animal Biology, Silberman Institute of Life Sciences, Hebrew University of Jerusalem, Israel.
Belenky
M
M
Cohen
S
S
Wagner
S
S
Schwartz
W J
WJ
D000818:Animals; D005904:Glial Fibrillary Acidic Protein / Q000032:analysis; D017403:In Situ Hybridization; D008027:Light; D008297:Male; D051379:Mice; D016253:Microscopy, Immunoelectron; D009419:Nerve Tissue Proteins / Q000096:biosynthesis / Q000528:radiation effects*; D009481:Neurophysins / Q000032:analysis; D019001:Nitric Oxide Synthase / Q000032:analysis; D016760:Proto-Oncogene Proteins c-fos / Q000096:biosynthesis / Q000528:radiation effects*; D013493:Suprachiasmatic Nucleus / Q000166:cytology / Q000378:metabolism / Q000528:radiation effects*; D014660:Vasoactive Intestinal Peptide / Q000032:analysis
D005904:Glial Fibrillary Acidic Protein; D009419:Nerve Tissue Proteins; D009481:Neurophysins; D016760:Proto-Oncogene Proteins c-fos; D014660:Vasoactive Intestinal Peptide; D019001:Nitric Oxide Synthase