A QUANTITATIVE ANALYSIS OF NORMAL NEURON POPULATION OF HYPOTHALAMIC MAGNOCELLULAR NUCLEI IN MAN AND OF THEIR PROJECTIONS TO NEUROHYPOPHYSIS

The supraoptic nucleus in man extends throughout the greater length of the hypothalamus and most of it is retrochiasmatic in location. It contains an average of 75,500 neurons, of which about two‐thirds are in its dorsolateral portion (SON‐dl) and one‐third in its combined dorsomedial and ventromedial portions. The average density of neurons in SON‐dl is 15,300 per mm3 and, unlike neuron frequency, is remarkably constant from specimen to specimen. The paraventricular nucleus has an average of 55,500 magnocellular neurons. In patients surviving one year or longer after hypophysectomy, there is retrograde loss of over 80% of neurons in both the supraoptic and paraventricular nuclei. Neuron loss occurs uniformly thrughout the length of each nucleus. Density decrease in SON‐dl is almost exactly proportional to decrease in neuron frequency. It is concluded from these observations that most of the neurons throughout the entire extent of both the supraoptic and paraventricular nuclei in man project to the posterior lobe of the neurohypophysis and that there are over 200,000 fibers in the hypophysial stalk. Copyright © 1969 The Wistar Institute of Anatomy and Biology