Electron microscope immunohistochemical localization of vasopressin in the hypothalamus and neurohypophysis of the normal and brattleboro rat

Using an immunoperoxidase technique at the ultrastructural level, vasopressin was localized in the axons of both the supraoptic and paraventricular nuclei, in the internal zone of the median eminence and the posterior pituitary but not in the perikarya of the neurosecretory neurons. A complete absence of histochemical reaction was found in the hypothalamo‐neurohypophyseal tract of the rat with hereditary hypothalamic diabetes insipidus (Brattleboro strain).