Early changes of blood-brain barrier and superoxide scavenging activity in rat cryogenic brain injury

Cryogenic brain injury results in blood-brain barrier (BBB) disruption which may be mediated in part by oxygen free radicals. In this study, sequential changes of BBB and endogenous superoxide scavenging activity were investigated in brains subjected to cryogenic injury. 92 male Wistar rats were sacrificed at 15, 30 minutes, 1, 2, 3, 4, 6, 24 and 48 hours after the lesion. The extent of BBB disruption was determined by quantitative assessment of Evans blue (EB) uptake based on extraction from tissue using dimethylformamide. Determination of endogenous superoxide scavenging activity in the injured brain was performed by electron spin resonance spectrometry using a spin trapping agent. Superoxide scavenging activity was significantly decreased within one hour after the injury relative to normal rat brain (p < 0.05, student's t test) persisting for at least 6 hours. The EB content in the lesioned hemisphere was significantly increased within one hour after the injury relative to the normal rat brain (p < 0.01) and continued to increase for 24 hours. In conclusion, early changes of BBB and endogenous superoxide scavenging activity in rat cryogenic injured brain indicate that BBB may be an early target for oxygen free radicals in cryogenic brain injury.