Effect of incomplete ischemia and reperfusion of the rat brain on the density and affinity of alpha-adrenergic binding sites in the cerebral cortex. Prevention of changes by stobadine and vitamin E.

The effect of incomplete 4 hr ischemia and subsequent 1 hr reperfusion of the rat brain on the density and affinity of alpha-adrenergic binding sites was investigated. To assess the involvement of oxygen-derived free radicals in the development of ischemic injury, we tested the effect of stobadine and vitamin E on putative changes of the binding parameters of alpha-adrenergic binding sites in ischemic and reperfused rat brains. Compared to the group of sham operated animals decreased density and increased affinity of [3H]dihydroergocryptine binding sites was found in cerebrocortical membranes of rats subjected to 4 hr incomplete ischemia and 1 hr reperfusion. The reduction of Bmax and Kd induced by ischemia and reperfusion of the brain was prevented by stobadine and vitamin E administration. Neither incomplete ischemia nor incomplete ischemia and subsequent reperfusion of the rat brain exerted significant effect on [3H]rauwolscine binding to alpha 2-adrenergic binding sites. Our results suggest that brain ischemia and reperfusion may affect the density and affinity of alpha 1- rather than of alpha 2-adrenergic binding sites. The beneficial effect of stobadine and vitamin E indicates that increased generation of oxygen free radicals might play a role in the development of these changes.