SHORT-TERM 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 moto r nucleus of the vagus nerve of male Wistar rats after induction of di abetes by streptozotocin. During the acute phase (3-7 days), degenerat ing electron-dense dendrites and axon terminals were dispersed in the neuropil. Degenerating dendrites were characterized by an electron-den se cytoplasm containing short segments of dilated rough endoplasmic re ticulum, swollen mitochondria and scattered ribosomes, while degenerat ing axon terminals were characterized by an electron-dense cytoplasm, clustering of small spherical agranular vesicles and swollen mitochond ria. Some of these degenerating axon terminals formed axodendritic syn apses 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 neur opil. During the late phase (9-12 months), a second wave of degenerati on occurred in the dorsal motor nucleus of the vagus nerve, similar to that of the acute phase. In addition to the degenerating dendrites an d axon terminals, several neuronal cell bodies with electron-dense cyt oplasm were observed. Numerous macrophages containing degenerating deb ris were also present in the neuropil. It is concluded that the ultras tructural changes in the dorsal motor nucleus of the vagus nerve are t he result of streptozotocin-induced diabetes.