Calcium stores contribute to AIS calcium during AP firing. A, left, Representative effect of ryanodine (20 μm) on AIS calcium. Right, Representative effect of sequential ryanodine and CPA (20 μm) application on AIS calcium. Linescan data presented as mean ± SE. B, Summary of the effects of ryanodine on AIS calcium. *p < 0.05, Kruskal-Wallis with Mann-Whitney U test post hoc. C, Summary of the effects of sequential application of ryanodine and CPA. n.s.: not significant.