The Dynamic Research Of The Opening Of Blood-brain Barrier At The Early Stage Of Severely Scalded Rabbits

Objective: Blood-brain barrier(BBB) is the body's basic structure to maintain homeostasis of the central nervous system. The opening of BBB after trauma will finally lead to the formation of cerebral edema. The purpose of our experiment was to use various methods to observe the opening of BBB at the early stage of severely scalded rabbits and investigate the earliest time and position of the opening,and its characteristics.Materials and methods: Healthy male New Zealand white rabbits were used to establish 50% TBSA Ⅲ°scalded model. 125I labeled bovine serum albumin (125I-BSA) was used as tracer to observe the earliest timepoint and position of opening of BBB after severe scald. 125I-BSA was used to measure the permeability of the BBB. 125I-BSA was injected intravenously before expriment. Control group and test group were sacrificed respectively by losing blood at each timepoint. The each tissue mass from anterior cortex,temporal lobe,posterior cortex,cerebellum,brain stem was obtained, weighed, and its radiation activity was counted. The results were analysised and compared with the changes of ultrastructure through microscopic and electronic microscopic. Using high resolution spiral CT (SCT), the average CT values of the interesting regions of brain parenchyma were measured when plain CT scan and contrast-enhanced CT were performed. The differences of CT values between distinct times were observed. Choosing the identical regions of double sides of the anterior cortex,temporal lobe,posterior cortex,cerebellum,brain stem to scan, the average CT values of the interesting region were measured by the software of CT. Observing the image changes of plain scan and contrast-enhanced scan, the opening of BBB in early scalded rabbits was found.Results: The pathologic features showed that blood vessels were congested and dilated, and the peripheral spaces of the vessels were wider at 2 hour after scald. Nervous cells and oligodendrocytes became to swell lightly at 3 hour after scald. All the peripheral spaces of the vessels were wider and nervous cells appeared vacuolation at 4 hour after scald. The results of electronic microscopic confirmed that BBB began to open at 2 hour after scald. The basal lamina and gial cell became to swell. The tight junction of blood vesselendothelial cell began to loose and vague at 3 hour after scald. The tight junction of endothelial cells began to vague at 4 hour after scald. The data demonstrated that severe scald could open BBB, and 125I-BSA intake began to remarkably increase at 2.5 hour in anterior cortex and cerebellum. 125I-BSA intake began to remarkably increase at 3 hour in all parts of the brain. The average CT values of contrast-enhancement scan in anterior cortex and cerebellum at 3 hour after scald were remarkably higher than those of unscald (P<0.05). The average CT values of contrast-enhancement scan in all the brain at 4 hour after scald were remarkably higher than those of unscald (P<0.05). CT image changes were found at 5 hour after scald, and those changes became more remarkably at 6 hour after scald. The CT image changes were found in 4 cases after contrast-enhanced at 5 hour after scald and increased to 11 cases at 6 hour, which showed the enhancement of brain parenchyma and cisterna ambiens. Conclusions: 1. Severe scald can gradually induce the opening of BBB. All the methods suggest that the earliest opening of BBB is at 2 hour after scald. And the position is cerebellum and anterior cortex. The BBB in each part of all brain opens at 3～4 hour after scald. The facts suggest that the impairment of BBB would aggravate in a diffuse and progressive way. 2. The opening of BBB was observed with 125I－BSA at 2.5 hour after scald. It is according with histological results. 125I－BSA is sensitive and precise to monitor the permeability of capillary.3. The contrast media molecule can enter into brain parenchyma after the opening of BBB. The changes of CT values at 3～4 hour after scald reflected the changes of ultrastructure of BBB. It is use...