Figure 4.

GTPγS-activated currents are markedly reduced in granule cells isolated from weaver and Girk2 null mutant mice, but only weaver granule cells show a change in K⁺ selectivity. Examples of GTPγS-activated currents recorded from wild-type (A), weaver (B), and Girk2 null (C) mutant mice are shown. Currents were elicited by voltage steps from −130 to +10 mV from a holding potential of 0 mV. The extracellular solution contained 20 mM K⁺ and 145 mM Na⁺. The GTPγS-activated current was obtained by subtracting the current recorded at the beginning of the whole-cell recording from the current recorded after GTPγS activation (see Fig. 2 legend). (D) The current-voltage plots show the strong rectification for +/+, +/−, and +/wv granule cells but a reversal potential for the +/wv granule cell that was more depolarized than that for the +/+ or +/− granule cells (arrows, Inset). (E) Bar graph shows the mean (±SEM) amplitude of the GTPγS-activated currents divided by the cell capacitance for +/+, +/wv, wv/wv, +/−, and −/− granule cells. Number of recordings is indicated above bars. ∗ indicates significant difference from +/+ (P < 0.05) as determined by one-way ANOVA followed by Dunn’s posthoc test on ranks.