Effects of cortical spreading depression on cortical blood flow, impedance, DC potential, and infarct size in a rat venous infarct model

A cortical venous infarction model has been evaluated as to the degree of r egional flow reduction and by studying effects of cortical spreading depres sion (CSD). Two adjacent cortical veins were occluded photochemically with rose bengal and fiberoptic illumination. Seven rats served to demonstrate e ffects on regional cortical blood flow using laser Doppler scanning. In 36 rats local CBF, DC potential, and brain tissue impedance were measured cont inuously for 75 min after vein occlusion, No, 3, or 10 CSD waves were induc ed by potassium chloride injection during the initial 75 min, Rats were com pared for spontaneous CSDs; baseline local CBF, CBF, and impedance response to CSD; and infarct volume. Seventy-five minutes after vein occlusion regi onal cortical flow in a 3.5 x 7-mm window was reduced to 34.3 +/- 13.2%. At 45% of the 840 measured locations in 7 rats flow was <40% baseline and at 27.3% <30%, indicating a widespread penumbra territory. During the initial 75 min 2.1 +/- 1.1 spontaneous CSDs were observed. There was a positive cor relation between the number of spontaneous CSDs seen acutely and infarction volume after 5 days. Moreover, brain injury was significantly increased in the group with 10 KCl-induced CSDs. A reduced 1CBF response and an oversho oting tissue impedance change during CSD were predictors of ischemic damage . This study demonstrates a CSD-related growth of the venous infarct. Secon d, the data indicate that flow after two-vein occlusion resembles that seen under penumbra conditions, allowing for studies of damage mechanisms respo nsible for infarct growth. (C) 2000 Academic Press.