Objective      To examine the alteration of aquaporin-4 (AQP4) expression and investigate the occurrence AQP4 internalization in rat brains with bacterial meningitis

so as to explore the possible role of AQP4 and its internalization in the brain edema of meningitis.        Methods      Group B hemolytic Streptococcus was injected into the cerebellar medulla pool of rat brain to establish a bacterial meningitis model. The brain water content

integrity of blood-brain barrier and expression of AQP4 were measured by wet and dry weight methods

Evans blue (EB) staining and Western blotting

respectively. Double immunofluorescence labeling was applied to detect the co-expression of AQP4 with early endosome antigen 1 (EEA1) as well as mannose-6-phosphate receptor (MPR)

respectively.       Results      Compared with control group

the brain water content in the model group increased [(81.4±2.3)% vs (77.3±1.6)%]

AQP4 expression increased [(57.41±7.00)% vs (44.50±7.45)%]

and Evans Blue content had no significant change (4.35±0.21 vs 4.27±0.33 μg/g). The co-expression of AQP4 with EEA1 and that of AQP4 with MPR were observed in meningitic rat brains.       Conclusion      AQP4 in rat brains is up-regulated in the bacterial meningitis model. Meanwhile

the internalization of AQP4 occurs in the model.