Figure 5.

Voltage pulse–induced fluorescence responses at different extracellular Na⁺ and K⁺ concentrations from oocytes coexpressing the α subunit construct sNaKα_{1, ØCys} together with sβ₁-S62C. (A–E) K⁺ titration in presence of Na⁺. Data were consecutively recorded from a single oocyte after changes to perfusion buffers with the following Na⁺/K⁺ contents: (A) 100 mM Na⁺ (no K⁺), (B) 99.9 mM Na⁺ and 0.1 mM K⁺, (C) 99.5 mM Na⁺ and 0.5 mM K⁺, (D) 99 mM Na⁺ and 1 mM K⁺, and (E) 95 mM Na⁺ and 5 mM K⁺. F shows the applied voltage protocol for all data traces shown in this figure. (G–J) K⁺ titration in presence of NMDG. Voltage pulse–induced fluorescence responses from a single oocyte experiment at different Na⁺/NMDG/K⁺ concentrations: (G) 100 mM Na⁺ (no K⁺, for control), (H) 99.9 mM NMDG and 0.1 mM K⁺, (I) 99.5 mM NMDG and 0.5 mM K⁺, and (J) 100 mM NMDG.