Little is known about mechanisms controlling the resolution of brain oedema.Early experiments showed that increased AQP4 expression was associated withoedema resolution,77,97–101 and in a vasogenic oedema model,Aqp4−/− mice developedsignificantly increased intracranial pressure compared to wild-type mice,confirming a role for AQP4 in oedema resolution.102. Here, AQP4 is linked to edema.