Morphological lesions in the brain preceding the development of postischemic seizures

This study explores how hyperglycemia and enhanced tissue lactic acidosis influence the density and distribution of ischemic brain damage. Ischemia of 10-min duration was produced in glucose-infused rats by bilateral carotid clamping combined with hypotension, and the brains were perfusion-fixed with formaldehyde following recirculation of 3, 6, 12 and 18 h. After about 24 h the hyperglycemic animals developed seizures, and at that time two groups were added, one fixed prior to, and one after the onset of seizures. Similar experiments were made on normoglycemic animals with recirculation times of 1.5 to 96 h. After fixation the brains were embedded in paraffin, subserially sectioned and stained with celestine blue/acid fuchsin. In both normo- and hyperglycemic animals, neurons in the dentate hilus of the hippocampal formation and in the thalamic lateral reticular nucleus showed early and dense neuronal necrosis. In neocortex, hippocampal CA1 sector and caudoputamen, hyperglycemia shortened the delay before damage occurred and markedly enhanced the damage. Specific for the hyperglycemic animals was damage of the substantia nigra, pars reticulata (SNPR), manifest already at the earliest recovery periods studied; this finding is discussed in relationship to the role SNPR is assumed to play in preventing spread of seizure discharge.