Short- and long-term effects of streptozotocin-induced diabetes on the dorsal motor nucleus of the vagus nerve in the rat.

The present study describes ultrastructural changes in the dorsal motor nucleus of the vagus nerve of male Wistar rats after induction of diabetes by streptozotocin. During the acute phase (3-7 days), degenerating electron-dense dendrites and axon terminals were dispersed in the neuropil. Degenerating dendrites were characterized by an electron-dense cytoplasm containing short segments of dilated rough endoplasmic reticulum, swollen mitochondria and scattered ribosomes, while degenerating axon terminals were characterized by an electron-defense cytoplasm, clustering of small spherical agranular vesicles and swollen mitochondria. Some of these degenerating axon terminals formed axodendritic synapses with seemingly normal as well as degenerating dendrites. During the mid phase (1-6 months), most of the degenerating neuronal profiles had been engulfed or removed by macrophages that infiltrated the neuropil. During the late phase (9-12 months), a second wave of degeneration occurred in the dorsal motor nucleus of the vagus nerve, similar to that of the acute phase. In addition to the degenerating dendrites and axon terminals, several neuronal cell bodies with electron-dense cytoplasm were observed. Numerous macrophages containing degenerating debris were also present in the neuropil. It is concluded that the ultrastructural changes in the dorsal motor nucleus of the vagus nerve are the result of streptozotocin-induced diabetes.