Focal ischemia in the cerebral cortex has an effect on the neurohypophysis. I. Ultrastructural changes in capillary vessels of the neurohypophysis after focal ischemia of the cerebral cortex.

OBJECTIVES In our investigations we have reported that photochemical reaction leading to brain ischemia can also be precipitated with visible light from a non-coherent light source. It was revealed that focal cerebral ischemia after photochemical reaction cause the alterations in the capillaries ultrastructure and perivascular spaces of the barrier-competent regions of the brain. The purpose of this study is to first characterize the ultrastructural morphological consequences of photochemically induced ischemia in the cerebral cortex on the capillaries of neurohypophysis as the barrier-free region of the brain. METHOD We used a model of ischemic brain damage due to obliteration of microvessels following the photochemical reaction. Rats were treated with an intravenous injection of rose bengal and irradiated from a halogen lamp source through an intact cranium to precipitate microvascular damage. Material for electron microscopic studies were sampled from the neurohypophysis 1 and 4 days after irradiation (4 animals in each group) in experimental group and 1 and 4 days after a rose bengal injection in control group. RESULTS Investigations in transmission electron microscopy revealed platelet aggregation on the endothelium preceded by its early ultrastructural damage. In the capillaries of the neurohypophysis, one and four days after irradiation, numerous microthrombi adhering to the damaged endothelium were present. The capillary vessels contained a continuous, rather than a fenestrated endothelium. The basement membrane was thickened, blurred and locally multiplicated. CONCLUSION Our results show that experimentally-induced thrombosis of cortical microvessels leads to alterations in the capillaries of neurohypophysis.