Quantitation of cerebral ischemic pressor response in dogs

Using a surgical technique designed to isolate the cerebral arterial circulation from the systemic and extracranial circulations and also a servomechanism devised to prevent blood volume shift between a donor dog and an experimental dog, the experimental dog's brain was perfused at a succession of controlled arterial pressures ranging from 140 to 0 mm Hg for the purpose of investigating quantitatively the steady-state response of the systemic arterial pressure (SAP) to stepwise changes of cerebral perfusion pressure (CPP) and cerebral blood flow (CBF). The interrelationships between CPP and SAP suggested a rectangular hyperbolic curve, but this same relationship was more clearly demonstrated when SAP was plotted against CBF. These findings suggest a chemical rather than pressoreceptor basis for the ischemic response. The peak values of ΔSAP/ ΔCPP in individual cases varied from 11.4 to 3.1 and averaged 7.7; thus the response was found to be four or more times as powerful as the carotid sinus pressorecepto...