Electron microscope immunohistochemical localization of neurophysin in the rat hypothalamus and pituitary

Abstract

In order to identify the organelles associated with neurophysin in neurosecretory neurons and axons, an electron microscopic immunohistochemical localization of this protein has been performed in the rat hypothalamus and posterior pituitary gland. Rabbit antiserum to human neurophysin II (which shows a cross-reaction with rat neurophysin) was used as antibody and the complex peroxidase-rabbit antiperoxidase (PAP) as the marker with unlabelled antirabbit globulin. PAP molecules indicating the presence of neurophysin were detected in the secretory neurons of both supraoptic and paraventricular nuclei, in axons of the internal layer of the median eminence and in the nerve terminals of the posterior pituitary gland. The reaction product was observed only over the secretory granules, all other organelles being negative. In the positive cells and axons, all the secretory granules present were usually labelled. These results demonstrate for the first time that neurophysin is associated with neurosecretory granules which also contain presumably either vasopressin or oxytocin.