A New Hypothalamic Pathway to the Median Eminence Containing Neurophysin and its Hypertrophy in Sheep with Natural Scrapie

THE hypothalamus is linked to the pituitary by two anatomically distinct neuronal neurosecretory pathways. The first, the hypothalamo-distal neurohypophysial system, commonly termed the supraoptico-neurohypophysial system (SNHS), arises in the “magno-cellular” cell bodies of the supraoptic nuclei (SON) and the paraventricular nuclei (PVN), whence their large axons descend via the internal infundibular zone to the posterior pituitary (Fig. 1)1,2. This system is characterized immunochemically by the neurophysins, the specific carrier-proteins for vasopressin and oxytocin3–6.