Noradrenergic innervation of vasopression-containing neurons in the rat hypothalamic supraoptic nucleus

The noradrenergic innervation of vasopressin (VP)-containing neurons in the supraoptic nucleus (SON) of the rat hypothalamus was studied electron microscopically by using double-labeling immunocytochemistry combining the pre-embedding peroxidase-anti-peroxidase method with post-embedding immunocolloidal gold staining. Noradrenaline-like immunoreactive axon terminals were found to make synaptic contacts with neurophysin II-like immunoreactive neurons in the SON. This study provides morphological evidence for noradrenergic control of neuronal activity of VP-containing neurons at the SON level.