Brain edema after middle cerebral artery occlusion. A comparison between normotensive and spontaneously hypertensive rats.

The right middle cerebral artery (MCA) was occluded either during 30 min or permanently, in normotensive Wistar Kyoto (WKY) and spontaneously hypertensive (SHR) rats. The rats were killed 2, 6 or 24 h later. Brain specific gravity, an indicator of brain edema, was determined on samples from the prefrontal, frontal, parietal and occipital cortex and the caudate nucleus. In SHR the brain specific gravity was significantly reduced in the right hemisphere at 2, but not at 6 or 24 h after a temporary occlusion. After permanent ligation, the specific gravity markedly decreased with time in the right hemisphere in SHR with significant difference from WKY, as well as from the left hemisphere, at all intervals. Our data support the concept that chronic hypertension aggravates ischemic brain edema after an arterial ligation.