Light Increases Fors-related Protein Immunoreactivity in the Rat Suprachiasmatic Nuclei.

摘要

A light-entrainable pacemaker located in the suprachiasmatic nuclei (SCN) appears to be responsible for the generation of a wide range of circadian physiological and behavioral rhythms in mammals. Bilateral destruction or surgical isolation of the SCN abolishes circadian rhythmicity in rodents and transplantation of fetal SCN tissue into the third ventricle of SCN-lesioned hosts restores rhythmicity. Fifteen minutes of bright, white light exposure at mid subjective night resulted in a marked increase in both the number and stain density of c-fos protein (Fos)-immunoreactive neurons in the suprachiasmatic nuclei (SCN). In all cells, peroxidase reaction product was confined to the nucleus. Most Fos-immunoreactive cells were concentrated in the ventrolateral third of the SCN, but a few cells were diffusely distributed along the dorsal border of the nucleus and into the surrounding hypothalamus. Along the rostro-caudal extent of the SCN, the greatest density of Fos-immunoreactive cells was found at a level approximately 300 - 400 m caudal of the rostral pole of the nucleus. The population of Fos-immunoreactive cells in the SCN lies within the terminal fields of both the retinohypothalamic and geniculohypothalamic tracts. A few Fos-immunoareactive cells were observed in the ventral lateral geniculate nucleus. The results suggest that retinal illumination induces transsynaptic c-fos expression in a select population of SCN neurons. Keywords: Protoncogene.