Inward rectification of the zebrafish αβδ channel isoform. (A) Sample ACh-activated single-channel currents recorded at the indicated potentials from cell-attached patches of Xenopus oocytes injected with either αβδ (left) or αβδε (right) RNA. (B) Whole oocyte ACh-activated macroscopic currents recorded at −80 mV and subsequently ramped from −80 to +80 mV over a 2-s period. Oocytes were either injected with αβδ (red) or αβδε (black). Leak currents recorded before ACh application are indicated in blue. (C) Current–voltage relations of macroscopic currents from αβδ (red; n = 5) and αβδε (black; n = 3) RNA-injected oocytes were normalized to peak current and fit with fifth-order polynomial (red) or linear curves (black).