Brain Edema Formation after Cryogenic Brain Injury in Rats

Kim, Kyung Hoon; Kwon, Jae Young; Kim, Hae Kyu; Baik, Seong Wan; Kim, Inn Se; Chung, Kyoo Sub

Abstract

The method of cryogenic brain edema has been used popularly for the study of experimental brain edema which is similar to vasogenic brain edema due to traumatic brain damage. After experimental cryogenic cerebral injury, severe focal brain contusion will be developed due to BBB breakdown and vasogenic cerebral edema formation. This study has been conducted to find out the index of other studies of brain edema by watching the time courses of cryogenic brain edema in rats. Forty five rats of either sex weighing 277+/-5 g(mean+/-SD) were freely drunken and fed till just before operation. Anesthesia was induced in a plastic box with 5% halothane in oxygen and then 1mg/kg of 0.5% urethane was injected into the peritonial cavity. The skull was exposed by a midline incision after infiltration of 2% lidocaine(total dose, <10 mg) and skull was reflected bilaterally. A funnel, an attached side of which was 5 mm in diameter, was attached on the left temporo-parietal area with epoxy glue. All rats were randomly selected into one of the two groups; Edema Group(40 rats) for the evaluation of brain edema and Barrier Group(5 rats) for the evaluation of integrity of BBB. Edema group was subdivided into 8 subgroup(5 rats in each group) according to the decapitation time in control, 15, 30, 45, 60, 90, 120, and 180 min. In edema group, cryogenic brain injury was made by pouring liquid nitrogen into the funnel for 60 seconds and then the brain was quickly removed at 0, 15, 30, 45, 90, 120, and 180 minutes after liquid nitrogen exposure. The cerebellum and brain stem caudal to the colliculi were discarded, and the cerebral hemisphere was separated. According to dry-weight method, the water contents of each hemisphere were measured. Data were analyzed by a one-way ANOVA test. In barrier group, the method of cryogenic brain injury was same as edema group and 0.5 ml of 3% Evans Blue was injected via right femoral vein just before exposure of liquid nitrogen. At 60 minutes after the cryogenic brain injury, the perfusion fixation was done and the brain was quickly removed and stored in the 10% formalin solution. The water contents of each hemisphere were proved to be similar with those of previous studies even through the conditions of dry-weight method were different. In this study, the amount of brain edema was increased till 90 minute after cryogenic brain injury and then decreased as time went by. From these results, the method of experimental brain edema after cryogenic brain injury is a good guidance of BBB breakdown and vasogenic brain edema study.