ARGININE VASOPRESSIN-LIKE AND OXYTOCIN-LIKE IMMUNOREACTIVE NEURONS INTHE HYPOTHALAMIC PARAVENTRICULAR AND SUPRAOPTIC NUCLEI OF STREPTOZOTOCIN-INDUCED DIABETIC RATS

This study describes ultrastructural and morphometric changes in the a rginine vasopressin (AVP)-like immunoreactive and oxytocin (OT)-like i mmunoreactive neurons in the hypothalamic paraventricular nuclei (PVN) and supraoptic nuclei (SON) of streptozotocin-induced diabetic rats a t 1-12 months post-diabetes. At 1-6 months post diabetes, both AVP-imm unoreactive and OT-immunoreactive neuronal somata were hypertrophied i n the PVN and SON. These neuronal somata contained highly dilated roug h endoplasmic reticulum in the cytoplasm. The reaction product for AVP as well as OT localization was dispersed throughout the cytoplasm and cell nucleus, but not within the nucleolus, Moreover, the reaction pr oduct appeared to be studded onto the ribosomes on dilated cisterns of the endoplasmic reticulum. At 9-12 months post-diabetes, both AVP-imm unoreactive and OT-immunoreactive dendrites contained dilated endoplas mic reticulum, autophagic vacuoles, lipid bodies, microtubules, membra nous bodies and occasionally swollen mitochondria. Labelled hypertroph ied axonal profiles containing neurosecretory granules, autophagic vac uoles, membranous bodies and tubulovesicular elements were also observ ed in the neuropil, Morphometric study showed that both AVP-immunoreac tive and OT-immunoreactive neuronal somata of the PVN and SON in the d iabetic rats were markedly hypertrophied at all the time intervals exa mined, It is concluded that the morphometric changes observed represen t hyperactivity of both AVP- and OT-immunoreactive neurons, while the concurrent ultrastructural changes observed at later stages may be ind icative of degeneration.