AQP4 and Alzheimer disease: Using a newly developed non-invasive imaging method capable of tracing exogenously applied substrates by magnetic resonance imaging (MRI) equivalent to positron emission tomography (PET), JJ vicinal coupling proton exchange (JJVCPE) imaging,5,6 we successfully demonstrated that water flow into the CSF system is regulated by aquaporin-4 (AQP-4), the water channel abundantly present on perivascular end feet of astrocytes.7 In this study, we demonstrated that this water flow is significantly reduced in senile plaque (SP) bearing transgenic Alzheimer disease (AD) model mice.