Fine structure of NPY-containing neurons in the lateral geniculate nucleus and their terminals in the suprachiasmatic nucleus of the rat.

Fine structures of neuropeptide Y (NPY)-like immunoreactive neuronal perikarya in the lateral geniculate nucleus and their terminals in the suprachiasmatic nucleus were investigated by peroxidase-antiperoxidase immunocytochemistry using male Wistar rats. NPY-like immunoreactive preterminal axons form both axo-somatic and axo-dendritic synapses on the neurons mainly located in the ventral portion of the suprachiasmatic nucleus. Almost all of them appeared as symmetrical synapses. Immunoreactive neuronal perikarya in the lateral geniculate nucleus show good development of cell organelles such as rough-surfaced endoplasmic reticulum and mitochondria. NPY-like immunoreactivity was distributed throughout the perikarya. The functional role of NPY-like immunoreactive terminals in the suprachiasmatic nucleus were briefly discussed.