Figure 2. Resting membrane potentials at selected [K⁺]_o in rat ventricular myocytes.

A, representative perforated patch recording from a quiescent right ventricular myocyte in response to selected changes in [K⁺]_o, between 2.5 and 15 mm. Increases in [K⁺]_o produced depolarization; while 2.5 mm [K⁺]_o caused hyperpolarization of the resting membrane potential. B, representative recording from a rat right ventricular myocyte at 5 and 0.5 mm [K⁺]_o. Note that, as expected, in 0.5 mm [K⁺]_o after an initial hyperpolarization, the myocyte depolarized, and fired a number of action potentials. Arrows indicate the start of application of each [K⁺]_o.