ONTOGENY OF FOS PROTEIN-LIKE IMMUNOREACTIVITY IN THE SUPRACHIASMATIC NUCLEUS

This study examined the normal development of neuronal activity in the suprachiasmatic nuclei (SCN) of rats between age 3-60 days, using Fos protein-like immunoreactivity (Fos-LI) as a marker. At age 3 days, Fo s-positive nuclei are sparsely distributed throughout the SCN. Between age 3-10 days, the density of labeled nuclei increases significantly. Fos-LI labeling is maximal at 10 days. Between age 10-14 days, the nu mber of labeled nuclei decreases and remains relatively constant there after, although the intensity of the reaction product diminishes as th e animal matures. By age 60 days, the number of Fos-LI labeled nuclei in the SCN is substantially decreased and is essentially the same as i n the 3-day-old rat. The appearance of Fos-LI nuclei in the SCN during development appears to reflect the development of visual system affer ents to the nucleus as well as the development of intrinsic SCN synapt ology. (C) 1995 Wiley-Liss, Inc.