Figure 4.

Effects of elevated [K⁺]_o and low pH on action potentials in muscles from adult rats. Data from the experiments are shown in Table II. (A) Effect of reduced pH on the number of fibers at 9 mM K⁺ that responded with an action potential (excitable fibers) when injected with a 100-nA depolarizing constant current pulse of 25 ms duration. (B–D) Representative traces of membrane depolarization and action potentials in response to a depolarizing constant current pulse in fibers at 4 mM K⁺ and normal pH (B), at 9 mM K⁺ and normal pH (C), and at 9 mM K⁺ and low pH (D). For other details, see legend to Table II.