Neuropeptide Y localization in the rat suprachiasmatic nucleus and periventricular hypothalamus.

Electron microscopic immunocytochemical localization of neuropeptide Y (NPY) was used to examine the morphology and synaptology of afferents in the rat suprachiasmatic nucleus and periventricular hypothalamus. NPY-like immunoreactivity in both areas is restricted to axon terminals which contain lucent, pleomorphic vesicles, occasional dense core vesicles and which establish asymmetric synaptic contacts with distal dendrites and spines. The data demonstrate that NPY-containing axon terminals in these two functionally distinct systems are of identical morphology and exert their effects upon neuronal activity via classical synaptic contacts.