Figure 6. Current flow through Ca_v1.1 does not initiate, but helps to sustain, plateau potentials in 9-AC treated muscle.

(A) The voltage protocol applied to FDB/IO fibers consisted of a ramp depolarization from −85 mV to +10 mV applied over 8 s. (B) A large inward current is present in wild-type muscle when Na⁺, K⁺, and Cl⁻ currents were blocked. (C) ncDHPR muscle fibers confirm the absence of inward Ca²⁺ current as there is only the linear change in current due to the changing command potential. (D) A plateau potential in a 9-AC treated wild-type muscle fiber. (E) A plateau potential in a 9-AC treated ncDHPR fiber.