Light-induced APs in Xenopus oocytes using the skeletal muscle Na⁺ channel subtype Na_v1.4. (A) Thirteen superimposed current-clamp recordings in oocytes expressing Na_v1.4 and β1-ChR2. (B) Eleven superimposed current-clamp recordings in oocytes expressing Na_v1.4, β1-ChR2, and K_v2.1. Coexpression of the voltage-gated K⁺ channel led to AP shortening and a less pronounced variability in AP duration and shape. For detailed statistics, see Table S1. The blue-light flash is indicated by an arrow.