Influence of profound hypothermia on the blood-brain barrier permeability during acute arterial hypertension

Abstract

In hypothermic rats with acute hypertension induced by intravenous injection of adrenalin, regional changes in blood-brain barrier permeability to macromolecules were investigated using Evans blue as indication. Evans blue albumin extravasation was determined as a macroscopic finding and a quantitative estimation with a spectrophotometer using homogenized brain to release the dye was also performed to evaluate the macroscopic findings. Five groups of rats were studied: Group 1: normothermia+acute hypertension; Group 11: hypothermia+acute hypertension; Group III: control hypothermia; Group IV: normothermia+hypotension; Group V: control normothermia. The rats were anaesthetized with diethyl-ether. Body temperature was lowered by submerging anaesthetized animals in an ice water bath. The colonic temperature was reduced to 20±1 °C. During adrenaline-induced acute hypertension the mean arterial blood pressure increased in both normothermic and hypothermic animals. Blood-brain barrier lesions were present in 40% of normothermic rats, and 60% of hypothermic rats after adrenaline-induced hypertension. Mean value for Evans blue dye in the whole brain was found to be 0.530±0.202 mg% in the normothermic rats and 0.752±0.256 mg% in the hypothermic rats during adrenaline-induced hypertension. This difference between normothermic and hypothermic rats was found to be statistically significant ( P<0.01). Our results showed that the extravasation of Evans blue albumin was most pronounced in the brains of hypothermic rats compared to normothermic rats after adrenaline-induced acute hypertension.