Compensatory adjustment in blood flow of the rabbit cerebral cortex during graded cerebral ischemia

The role of the bilateral internal carotid and vertebral arteries in supplying cerebral cortex tissue blood flow (CTF) and the compensatory adjustment in CTF during graded cerebral ischemia were studied to determine the relationship to the increase in systemic arterial pressure (SAP) in anesthetized rabbits. CTF was recorded continuously by using Peltier stacks placed on both sides of the surface of the cerebral parietal cortex. Occlusion of the bilateral internal carotid arteries caused a decrease in CTF to 81.9% of the control value for the right hemisphere, and 83.5% of that for the left. Occlusion of the bilateral vertebral arteries produced no appreciable change in CTF. Compensatory adjustment in CTF was incomplete, i.e., CTF was reduced to a lower level, in the range of internal carotid flow (ICF) from 2 to 6 ml/min, and was severely reduced at 1 and 0 ml/min. The relationships between ICF and SAP, and ICF and CTF formed rectangular hyperbolic curves. No significant difference was observed between the decreases in CTF obtained before and after bilateral sectioning of the cervical sympathetic trunks. The relationship between SAP and CTF was described by a linear regression equation. These results indicate that the internal carotid arteries play a much more important role in supplying CTF than the vertebral arteries, that SAP rises in inverse proportion to the decrease in CTF, and that the cervical sympathetic trunks do not influence the compensatory adjustment in CTF caused by cerebral ischemia.