Identification of neuropeptide Y immunoreactivity in the suprachiasmatic nucleus and the lateral geniculate nucleus of some mammals.

The distribution of neuropeptide Y (NPY) immunoreactivity in the suprachiasmatic nucleus (SCN) and the lateral geniculate nucleus (LGN) of 5 kinds of mammals was studied using the peroxidase-anti-peroxidase method. In the SCN of the rat, hamster, chipmunk and cat, NPY-immunoreactive fibers were detected, particularly in the ventral part. In the 3 rodents and the cat, the somata and fibers of NPY-immunoreactive neurons were observed in the LGN. However, immunoreactive structures were not found in the SCN or LGN of the monkey. These results indicate that NPY immunoreactivity in the monkey LGN-SCN tract is absent.