Functional Significance of Two Types of Neurosecretory Granules in the Posthypophysis: Ultrastructural and Cytochemical Approach

Since elementary neurosecretion granules and two neurohormones, vasopressin and oxytocin, have been shown to occur in the hypothalamo- posthypophyseal system, the question has been raised whether different types of granules, fibers, and neurons correspond to each of the two hormones. This view was initially supported by biochemical data from ultracentrifuged cellular fractions; two types of granules and fibers containing vasopressin and oxytocin respectively could be separated.