Figure 8. Inhibition of outward currents in the WT Kir2.1 channel by internal 1 mM Mg²⁺ and 10 μM SPM.

(a) Sample sweeps demonstrating inhibition of WT Kir2.1 currents in the same patch by internal 1 mM Mg²⁺, 10 μM SPM, and concomitant 1 mM Mg²⁺ and 10 μM SPM in symmetrical 100 mM K⁺ (see Fig. 1a for the pulse protocol). The dotted lines indicate the zero current level. (b) The experiments were performed in symmetrical 100 mM extracellular K⁺ for the WT Kir2.1 channel. The relative currents are defined in the same way as that in Fig. 1. Note the stronger inhibitory effect (smaller residual currents) with 10 μM SPM than 1 mM Mg²⁺, and the even stronger effect (even smaller residual currents) with the concomitant presence of both 1 mM Mg²⁺ and 10 μM SPM. * and **p < 0.05 and <0.005, respectively, by student’s independent t–test. (c) The experiments were performed in external 20/ internal 100 mM K⁺ conditions for the WT Kir2.1 channel. The relative currents are defined in the same way as that in Fig. 1. The protocols were the same as that in Fig. 1a. The blocking effect of 1 mM Mg²⁺ is gradually increased, whereas the blocking effect of 10 μM SPM is gradually decreased, from +20 to +100 mV.