AQP4 and transient ischemic attack: In a mouse model of transient cerebral ischemia, AQP4 expression was rapidly up-regulated in perivascular end-feet, reaching the first peak after 1 hour (h) coinciding with early cerebral swelling in the core and border of the lesion, and the second peak in the penumbra after 48 h correlating with the degree of brain swelling (Ribeiro Mde et al., 2006).