The hypothalamo-neurohypophysial system in streptozotocin-diabetic rats. Ultrastructural evidence for neuronal alterations in the supraoptic and paraventricular nuclei and in the neurohypophysis.

The ultrastructure of the hypothalamo-neurohypophysial system of rats was examined 8 weeks after streptozotocin-induction of type I diabetes. These studies provided evidence for numerous neuronal alterations to the hypothalamo-neurohypophysial system in streptozotocin-diabetic rats. Changes were observed in the somata, dendrites and axons of both the supraoptic and paraventricular nuclei as well as in axon profiles in the neurohypophysis. Many of these changes suggest an increased activity of the hypothalamo-neurohypophysial complex, with increased synthesis of neurohypophysial hormones in the hypothalamus together with depletion of neurosecretory granules in axons in the neurohypophysis. Some degenerative changes, however, were also observed. It is proposed that chronic dehydration and hypoxia in diabetes may contribute to the ultrastructural reorganization of the hypothalamo-neurohypophysial complex in streptozotocin-diabetic rats.