Development and Evaluation of an Experimental Model for the Study of the Cerebral Circulation in the Unanesthetized Goat

An animal model has been developed for the continuous measurement of total cerebral blood flow in the unanesthetized, unrestrained goat. We selected the goat because each internal maxillary artery, a branch of the external carotid artery, provides the total blood flow to each hemisphere via the rete mirabile. After the occlusion of the extracerebral vessels of the internal maxillary artery with thrombin, an electromagnetic flow transducer was chronically implanted on this artery, distal to the temporal artery, to measure hemispheric blood flow. Reproducible measurements of cerebral blood flow were obtained in ten unanesthetized goats for periods ranging between two weeks and five months. The mean cerebral blood flow for the ten goats was 133 ± 5 ml/min/100 gm tissue at an average mean aortic pressure of 91 ± 3 mm Hg, heart rate of 79 ± 3 beats/min, arterial PCOCO2 of 31.4 ± 1.0 mm Hg, P02 of 76.6 ± 1.7 mm Hg, and pH of 7.48 ± 0.02. The present experimental preparation allows cerebrovascular hemodynamics to be evaluated under near-normal conditions and is suitable for physiological and pharmacological studies in normal and abnormal states.