ATP1A2 and migraine disorder: The numbers of astrocytes with elevated Ca2+ concentrations in Atp1a2+/− (11.0 ± 2.8 astrocytes) were larger than those in wild‐type mice (5.7 ± 2.5 astrocytes) after induction of cortical spreading depression (which is closely associated with migraine) by application of KCl.