The hypothalamo-neurohypophysial system in streptozotocin-diabetic rats: ultrastructural and immunocytochemical evidence for alterations of oxytocin- and vasopressin-containing neuronal profiles.

The hypothalamic paraventricular and supraoptic nuclei and the neurohypophysis of rats were investigated 8 weeks after streptozotocin (STZ)-induction of type 1 diabetes. Vasopressin (VP)- and oxytocin (OT)-containing neuronal profiles were examined using the pre-embedding peroxidase-antiperoxidase technique for electron microscopy. Ultrastructural alterations were observed in the somata, dendrites and axons of VP- and OT-labelled profiles. There was no evidence, however, for alterations in the synapses associated with VP- or OT-labelled somata, dendrites and axons. The results indicate that both VP- and OT-containing neuronal profiles are involved in the ultrastructural reorganisation of the hypothalamo-neurohypophysial complex during diabetic conditions. Depletion of VP- and OT-containing axon profiles in the neurohypophysis may suggest increased release of both neurohypophysial hormones in STZ-induced diabetes.