Figure 4. Cation dependency of AA-induced currents.

(a) Example of substrate-induced currents in an AaSlif-expressing oocyte after application of 1, 3 and 10 mM of L-Arg in 98 Na⁺ (green line) and 98 K⁺ (red line) buffers (containing identical concentrations of Cl^– and other ions). Black arrow indicates washing after L-Arg application with initial buffer saline. Grey arrows indicate accelerated recovery after re-application of 3 or 1 mM of L-Arg (for 98 K⁺ buffer only). (b) Background-subtracted I/V plots of AaSlif-expressing oocytes in 98 Na⁺ and 98 K⁺ buffers with three different concentrations of L-Arg (insert). (c) I/V plot calculated by subtraction of the current values measured in 98 K⁺ from those in 98 Na⁺. Results show no significant dependency of current on L-Arg concentration. (d) L-Phe-induced currents in four different buffers. Results show that substitution of Na⁺ with Li⁺ and NMDG⁺ ions reduced substrate-induced currents, whereas the substitution with K⁺ reversed the current. (e) I/V plots acquired from the same oocyte as in d with different cation compositions, as colour-coded in insert. (f) I/V plots calculated by subtraction of current values measured in 98 K⁺ and 98 Li⁺ buffers from those in 98 Na⁺ buffer.