Ultrastructural immunocytochemical characterization of isotocin, vasotocin and neurophysin neurons in the magnocellular preoptic nucleus of the goldfish.

We describe the ultrastructural localization of isotocin, vasotocin and neurophysin in the magnocellular preoptic nucleus of the goldfish. With the aid of immunocytochemical techniques, we see staining both in classical neurosecretory granules and in diffuse agranular form throughout somata and processes. Signs of cellular and synaptic interactions between chemically identified neurons include axon terminals which contain vasotocin immunoreactivity and membrane specializations (puncta adhaerentia) between adjacent somata. Our investigations provide an anatomical basis for neuroendocrine and neurotransmitter-like functions of peptidergic neurons in the teleost preoptic nucleus.