EDEMA-RELATED TISSUE-DAMAGE AFTER TEMPORARY AND PERMANENT OCCLUSION OF THE MIDDLE CEREBRAL-ARTERY

Eleven adult spontaneously-hypertensive male rats (SHR) were studied 2 2 h or 7 days after a 2 h unilateral occlusion of the right middle cer ebral artery (MCA). Another 11 SHR were studied after 24 h or 7 days o f permanent MCA ligation. The brain infarcts were significantly larger (P < 0.05) after permanent occlusion than after a 2h occlusion. More extensive and widespread vasogenic oedema, emanating from the infarcts , was visualized immunohistochemically in the temporarily-ligated anim als and the relative number of astrocytes in their contralateral hemis pheres was greater, thereby indicating that the vasogenic oedema influ ences the degree of gliosis. An immunopositivity for albumin but not f or fibrinogen extended via the white matter into the ipsilateral thala mic nuclei, where cytolytic nerve cell damage, severely shrunken and k aryorrhectic nerve cells as well as gliosis were found one week after permanent and temporary MCA ligation. The histological changes in the thalamus indicated a difference in timing between lateral and medial p arts of the lesion as well as between temporarily- and permanently-lig ated SHR. These findings together with the close spatial correlation w ith albumin immunoreactivity indicate that the spread of extravasated plasma constituents or degradation products with the oedema bulk flow from the infarct influences the timing, character and extent of thalam ic lesions after cerebral infarction.