In the pre-ischemic astrocyte endfoot (left), NCX1 operates in calcium extrusion mode, and SUR1-TRPM4 is absent. In the post-ischemic astrocyte endfoot (right), newly increased SUR1-TRPM4 mediates Na+ influx (#1) which drives Ca2+ influx through the calcium entry mode of NCX1 (#2). The increase in Ca2+ activates CaM (#3), which stimulates trafficking of AQP4 to the cell membrane (#4), where AQP4 facilitates water influx that contributes to swelling.