Effects Of Cervical Lymph Blocked On Blood-brain Barrier Permeability In Rats

Objectives To investigate permeability changes and its possible mechanisms of blood-brain barrier (BBB) in cerebral cortex and hippocampus after blocking cervical lymph, and analysis correlation between the BBB-permeability changes and cerebral edema.Methods Male-Wistar rats (250-300g, n=195) were randomizied into three groups:normal group (having no any treatment), operation group (blocking cervical lymph by using Casley-Smith method) and sham-operation group (only using the method of separating cervical lymph). Every group was set into six time points:1,3,5,7,14 and 21 days after operation.The following indexes were detected at the above time points:changes of water content in brain tissue (weigted by dry-wet method),BBB permeability(measuring Evans blue content of the brain tissue and observing La3+ and BBB ultrastructure under electron microscope), serum S-100B concentration (measured by ELISA) and expression levels of MMP-9 (evaluated by immunofluorescence) in cerebral cortex and hippocampus.Results1.The changes of all-detected indexes in cerebral cortex were consistent with these in hippocampus.2.Evans blue (EB) contents in sham-operation group and operation group increased at 1 day, but had no significant statistics difference compared with the normal group. Sham opera-tion group restored to the normal level at 3 day. The EB content in operation group increased at 3,5 and 7 day(there was marked statistical difference(p<0.05) compared with the normal group)and restored the normal level at 14 day.3.Telescope observation:La3+ didn't occur in extravascular position in all groups. The BBB-ultrastructure changes only appeared in operation group:Increased-pinocytotic vesicles in endothelial cells and edema in basement membrane and astrocyte. The above changes occurred at 3 day, aggravated at 5 day and abated at 7 day.4.Serum S100B concentration had no obvious changes in different groups.5. Expreeion levels of MMP-9 in sham-operation group and operation group increased at 1 day but had no significant difference compared with the nomal group. That in operation group had two peak values (at 3 and 14 day) and there was significant difference (p<0.05) compared with the same time points in sham-operation group and nomal group. Expreeion levels of MMP-9 restored to the normal level at 3 day (in sham-operation group) and at 21 day (in operation group), respectively.6. Water content of brain tissue in sham-operation group and operation group increased at 1 day but had not significant difference compared with the nomal group. That in operation group markedly incread at 3,5 and 7 day and there was significant difference (p<0.05) compared with the same time points in sham-operation group and nomal group. Water content of brain tissue restored to normal level at 3 day (in sham-operation group) and at 14 day (in operation group), respectively.7.There was a high correlation between EB content changes and cerebral edema in cerebral cortex and hippocampi (Pearson Correlation:r=0.761, r=0.773,respectively); but no correlation between expreeion levels of MMP-9 and cerebral edema (Pearson Correlation:r=-0.246 (P=0.595),r=-0.175 (P=0.707), respectively).ConclusionsOur study confirmed that cervical lymph blockade had no obvious effect on BBB permeability. The increased-EB content at 3 and 5 days after operation was mainly caused by serum protein accumulation in brain tissue, which indicated that the pathway of brain lymphatic drainage played an important role in removing brain protein and maintaining micro-environmental stability. A high correlation between EB content and cerebral edema...