AQP4 and Stroke: Studies of mice that suffer a loss of perivascular AQP4 following genetic deletion of α-syntrophin have shown that this pool of AQP4 is involved in a number of critical functions including potassium homeostasis (Amiry-Moghaddam et al., 2003b) and edema formation following stroke (Amiry-Moghaddam et al., 2003a), or hyponatremia (Amiry-Moghaddam et al., 2004b).