KCNN4 and Stroke: However, an observation period of 4 h was chosen due to (1) studies by our research group indicating significantly enhanced endothelial KCa3.1 channel signaling 2 and 4 h after cardiac arrest,11, 12 and (2) KCa3.1 channel inhibition showing a significant reduction in cerebral edema 4 h after stroke in rats.13