The influence of phenylephrine-induced hypertension during focal cerebral ischemia on the formation of brain edema.

The authors investigated the effects of phenylephrine-induced hypertension on the development of cerebral edema and neuronal dysfunction during focal cerebral ischemia. Mean arterial pressure was increased by 25-30 mm Hg immediately after middle cerebral artery occlusion (MCAO) in anesthetized rats. The increase was maintained for 3 h, at which time the brains were harvested and sectioned along coronal planes spanning the distribution of the MCA. The specific gravity (SG) was determined in specimens of cortex and subcortex. Brain sections adjacent to those used for SG measurement were incubated in 2,3,5-triphenyltetrazolium (TTC). There was edema formation in both groupsipsilateral to MCAO. However, in some regions, there was less edema accumulation in the induced hypertension group than in normotensive control animals. In adjacent regions, the area of reduced or absent TTC staining was also significantly less in the induced hypertension group. The data indicate that, in this model, induced hypertension established soon after the onset of ischemia can serve to reduce the area of histochemically detectable neuronal dysfunction, and that not only is edema formation not aggravated, but it is actually reduced.