This chapter contains sections titled: Introduction Astrocyte Endfeet and BBB Maintenance Astrocyte Endfeet and BBB Development Astrocyte Endfeet and BBB Damage The Role of Aquaporins in BBB Maintenance and Brain Edema AQP Expression and Functional Roles The Role of AQP4 in Brain Edema DMD Animal Models The α-Syntrophin Null Mice The Effect of Lipopolysaccharide on AQP4 Expression AQP4 in Astrocytomas AQP4 Expression in Astrocyte-Endothelial Cocultures References