Epilepsy is characterized by the abnormal activation of neurons in the cerebral cortex, but the molecular and cellular mechanisms contributing to the development of recurrent seizures are largely unknown. Recently, the critical involvement of astrocytes in the pathophysiology of epilepsy has been proposed. However, the nature of plastic modulations of astrocytic proteins in the epileptic cortex remains poorly understood. In this study, we utilized the zero magnesium in vitro model of epilepsy and examine the potential molecular changes of cortical astrocytes focusing specifically on endfeet where specialized biochemical compartments exist. We find that continuous epileptic activation of neurons for 1 hour decrease the expression level of β-dystroglycan (βDG) in acute cortical brain slices prepared from mice. This change is completely abolished by the pharmacological blockade of NMDA-type glutamate receptors as well as MMP inhibitors. Consistent with the specific localization of βDG at astrocytic endfeet where it plays a pivotal role in anchoring endfeet -enriched proteins in astrocytes, the downregulation of βDG is accompanied by a decrease in the expression of AQP4 but not laminin. Importantly, this downregulation of βDG persists for at least 1 hour, even after the apparent recovery of neuronal activation. Finally, we show that this downregulation of βDG is associated with the impairment of the diffusion blockade function of endfeet at the blood-brain interface. These results suggest that sustained βDG dysregulation at astrocytic endfeet occurs in the epileptic cerebral cortex and may contribute to the pathogenesis of epilepsy.