Identification of the vasopressin-neurophysin II and the oxytocin-neurophysin I producing neurons in the bovine hypothalamus.

Immuno-enzyme histochemical investigations on the bovine hypothalamus showed that vasopressin and oxytocin are synthetized in separate neurons. Moreover, it was found that the vasopressin-producing neurons are identical with the neruophysin II-producing neurons, while the oxtocin producing neurons correspond with the neurophysin I-producing neurons. From this result it is concluded that, in the species studied, neurophysin I is the carrier protein of oxytocin and that neurophysin II is the carrier protein of vasopressin. The bovine vasopressin-neurophysin II producing neurons and the oxytocin-neurophysin I producing neurons are both present as well in the suparoptic nuclei as in the paraventricular nuclei. In the supraoptic nuclei, the vasopressin-neurophysin II neurons predominate in number; in the paraventricular nuclei, the oxytocin-neurophysin II neurons predominate. The two kinds of bovine neurosecretory neurons are partly localized in separate areas. Moreover, the vasopressin-neurophysin II neurons and the oxytocin-neurophysin I neurons show distinct morphological differences.