The effect of cerebral ischemia on the ultrastructure of the hypothalamo-neurohypophysial system of the mongolian gerbil. The supraoptic and paraventricular nuclei.
The results of ultrastructural studies of the nucleus supraopticus (SON) and n. paraventricularis (PVN) of male mongolian gerbils subjected to experimental cerebral ischemia induced by 10 min bilateral occlusion of the common carotids are reported. Marked alterations concerned endocrine neurons, some neurosecretory axons and synaptic terminals as well as astroglia cells. Basing on the electron density of cytoplasmic ground, two varieties of endocrine neurons, that is 'light' and 'intermediate', were designated in both SON and PVN nuclei. These findings suggest that during cerebral ischemia the SON and PVN neurons become activated (Golgi complex and granular endoplasmic reticulum enlargement) and that they represent different phases of secretory cycle of a single cell type. However, in SON nucleus some neurons were probably damaged because they had the appearance of decidedly 'dark' cells. With respect to some neurosecretory axons, the finding of externally lying lamellar whorls indicates ischemic injury of the axons. Similar significance may be attributed to some synaptic terminals which showed an increased polymorphism of synaptic vesicles and vesicular aggregation. There was marked swelling of perivascular astroglia cells and change of their cytoplasm in both SON and PVN nuclei. Moreover, the swollen astroglia cells contacted those 'dark' neurons in SON nucleus. The present study indicates that SON and PVN nuclei are highly sensitive to application of cerebral ischemia. At the same time perivascular injury may suggest involvement of astroglia cells in the production of subsequent changes in the SON and PVN neuropil.
D000818:Animals; D001253:Astrocytes / Q000648:ultrastructure; D002545:Brain Ischemia / Q000473:pathology*; D005849:Gerbillinae / Q000033:anatomy & histology*; D008297:Male; D008854:Microscopy, Electron; D009474:Neurons / Q000648:ultrastructure; D010286:Paraventricular Hypothalamic Nucleus / Q000648:ultrastructure*; D013495:Supraoptic Nucleus / Q000648:ultrastructure*