(A) IOS of CSD induced by local KCl application (Puff) in slice of wt/wt animal with K⁺ sensitive and LFP electrodes. Scale bar: 500 μm. (B) Traces of K⁺ sensitive recording (top) and LFP signal (bottom) during CSD for slices of wt/wt (left) and mut/wt animals (right). CSD-recording elicited by KCl-application (arrow) (left). Averaged [K⁺]_e dynamics before and during CSD (wt/wt: 21 slices; mut/wt: 30 slices) (right). Magnified boxes indicate AUC from point at which K⁺ signal left baseline (threshold: +0.1 mM) to inflection-point of [K⁺]_e curve (see Supplemental Figure 5B). (C) Success rate of CSD induction in slices of both genotypes (wt/wt: n = 43 slices from 12 animals [43/12]; mut/wt: 41/11; P < 0.001; Fisher’s exact test). CSD failed category includes CSDs that aborted before reaching K⁺ and DC electrodes. (D) Propagation velocity was increased in mut/wt compared with wt/wt animals (wt/wt: 22/10; mut/wt: 31/11; ***P < 0.001; Mann-Whitney rank sum test). (E) [K⁺]_e at inflection point of K⁺ signal (determined as in Supplemental Figure 5B) and maximum [K⁺]_e (right) during CSD. [K⁺]_e was increased in slices of heterozygous compared with WT animals (wt/wt: 22/10; mut/wt: 31/11; **P < 0.01, ***P < 0.001; Mann-Whitney rank sum test). (F) [K⁺]_e increased earlier in slices of heterozygous compared with WT animals. Time at which [K⁺]_e started to increase to inflection point of K⁺ signal (left) and from inflection point to maximum peak (right). Initial rise of [K⁺]_e started earlier in mut/wt compared with wt/wt animals (wt/wt: 22/10; mut/wt: 31/11; *P < 0.05; Mann-Whitney rank sum test). Time from inflection point to peak concentration was not different between genotypes (wt/wt: 22/10; mut/wt: 31/11; Mann-Whitney rank sum test). (G) AUC from start of [K⁺]_e increase to inflection point of K⁺ signal (as shown in B) increased in slices of mut/wt compared with wt/wt animals (wt/wt: 22/10; mut/wt: 31/11; **P < 0.01; Mann-Whitney rank sum test).