AQP4 and infectious meningitis: Furthermore, while in the brain of sham control animals with a functioning glymphatic system, AQP4 expression is homogeneously expressed along the area between the astrocytic end feet and BBB vascular endothelium, in the brain of meningitis-affected rats in which the glymphatic system is malfunctioning, AQP4 expression is focal on astrocytic cells and far from any colocalization with the BBB endothelium (Fig. 2E).