Computer-Regulated Constant Pressure Ischemia in the Rat: The Animal Model

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Abstract
A system permitting computer control of partial ischemia in the normotensive rat brain was developed. Right carotid cannulation and bilateral subclavian artery occlusion made the input of blood to the brain dependent solely on left carotid artery flow. Perfusion pressure was controlled by partial compression of this artery with a balloon. The system can produce a range of partial ischemic states maintaining perfusion pressures from 4 to 20 mm Hg. The adequacy of the servo-control system was evaluated in greater detail at requested perfusion pressures of 7 and 12 mm Hg in 14 male Sprague-Dawley rats (300–450 g). Experimentally obtained cerebral perfusion pressures of 6.84 (SD = 0.25, n = 7) and 11.72 (SD = 0.89, n = 7) mm Hg, respectively, demonstrate the efficacy of the system. CBFs were concurrently measured at four separate bilaterally symmetric anatomic sites (cortex, hippocampus, thalamus, and substantia nigra). Significant intra- and interhemispheric differences were found to exist, with regional flows monitored ipsilaterally to the carotid balloon exceeding those of the opposite hemisphere. In summary, this acute model of cerebral ischemia permits control of perfusion pressure over the entire critical partial ischemic range.