Tolerance of the cerebral venous system to retrograde perfusion pressure in focal cerebral ischemia in rats.

Using quantitative double-tracer autoradiography, we examined the tolerance of the rat cerebral venous system in focal cerebral ischemia to retrograde perfusion pressure into the inferior cerebral vein. At perfusion pressures of less than 150 mm Hg, there was no significant change in local cerebral blood flow (LCBF) and blood-brain barrier (BBB) permeability. At pressures of greater than 170 mm Hg, significant changes occurred in BBB permeability in the superficial cortical layers and there was a mild reduction of LCBF. In the group of rats subjected to 200 mm Hg perfusion pressure, the change in BBB permeability extended to the entire cortical zone and significant reduction of LCBF occurred. Our results indicate for the first time that during conditions of focal cerebral ischemia, the rat cerebral venous system can tolerate up to 150 mm Hg of retrograde perfusion pressure into the cerebral venous system without any change in BBB permeability or in LCBF. However, progressive change in BBB permeability and reduction in LCBF occur once the perfusion pressure exceeds 170 mm Hg. This finding may permit more efficient delivery of cytoprotective agents into ischemic tissue.