Focal cerebral ischemia in chronic hypertension: no protection by (R)-phenylisopropyladenosine.

The effects of the adenosine agonist, (R)-phenylisopropyladenosine on focal cerebral ischemia induced by middle cerebral artery occlusion were investigated in spontaneously hypertensive rats. The drug was given 30 min before occlusion and each hour thereafter for 6 h. The neurological status of the rats was estimated 2, 24 and 48 h after occlusion. Infarct volumes were measured 48 h after occlusion (Cresyl violet-stained sections). (R)-Phenylisopropyladenosine did not significantly reduce infarct size, nor did it modify the neurological score. As there is considerable evidence of the neuroprotective effects of adenosine in normotensive rats, the present results may be due to a more abrupt reduction in cerebral blood flow in the territory surrounding the ischemic core, where neuroprotection could be expected, in the spontaneously hypertensive rat strain. Consequently, neuroprotection may be more difficult when focal cerebral ischemia is associated with hypertension.