Localization of Regions Mediating the Cushing Response in CNS of Cat

Abstract

THAT an acute elevation of intracranial pressure results in a rise of the systemic blood pressure and a fall of heart rate has been known for many years.^1-3In 1902, Cushing^4,5first demonstrated the quantitative nature of this response, showing that it was graded and occurred when the pressure within the head exceeded that of the systolic blood pressure. Furthermore, the response he observed was reversibly abolished by instilling cocaine into the cisterna magna. Cushing speculated that ischemia of the brain stem was the stimulus for the response and that it was in some manner mediated by the caudal brain stem. Since his report, the vasomotor phenomenon he described has become known as the Cushing "reflex." Because the reflex nature of the response has never been clearly established, however, in this paper it will be referred to as the Cushing response. It was never proved by Cushing, nor