Abstract
We investigated whether or not there are differences in the effects of phenylephrine-induced hypertension, with changes in its duration and extent, on the CBF, brain energy metabolism and brain parenchymal specific gravity following transient forebrain ischemia in gerbils. Gerbils were randomly assigned to one of the following 6 treatment groups : 15 mild-HT group (n=14); 25 mmHg increase in MABP by treatment with phenylephrine for 15 min, 30 mild-HT group (n=14); for 30 min, 60 mild-HT group (n= 14); for 60 min, 15 severe-HT group (n=14); 45 mmHg increase in MABP for 15 min, hypotension group (n=14); 30 mmHg decrease in MABP by exsanguination for 15 min at 30 min after reperfusion, and control group (n=14), without phenylephrine treatment. The CBF was measured continuously and the brain specific gravity was evaluated at 120 min after reperfusion. The sequential changes in brain energy metabolism, as indicated by the PCr/Pi ratio, β-ATP/Pi ratio and pHi, were also determined and were found to return to the preischemic level at 120 min after reperfusion. The recovery in brain energy metabolism was more rapid in the 15 mild-HT group, and the brain specific gravity was also greater in this group. The 15-min mild induced hypertension regime was most suited to the recovery of the brain energy metabolism which was associated with an increased CBF and without exacerbation of brain edema. In contrast, the 30- and 60-min mild induced hypertension and 15-min sevee induced hypertension regimes worsened the recovery of the brain energy metabolism and exacerbated brain edema. These findings clearly demonstrate differences in the beneficial effects of phenylephrine-induced hypertension, with changes in its duration and extent, on ischemic brain injury following transient forebrain ischemia.
