Figure 4 of
Zhang, Mol Vis 2001;
Figure 4. RA effect on Ca2+ gating of HGJ channel activity
A: Outward current was elicited by external Ca2+ concentration switch from 2 mM to 0 mM at a constant holding potential of 30 mV in an H-2 type horizontal cell. When the current was stable, the cell was exposed to 100 mM Ca2+ and the current dropped from 484 pA to 269 pA (-215 pA). After washout, 0.3 mM at-RA produced a 114 pA reduction. In the presence of RA, 100 mM Ca2+ produced an additional 95 pA inhibition for a total during coapplication of 209 pA. Each point represents the mean current from a 3 s interval of recording. B: Normalized dose inhibition relationships for Ca2+ inhibition of HGJ channel currents in the absence and presence of 0.3 mM at-RA. Each point is an average from 4 to 6 cells and smooth curves were fit with the Hill equation. RA shifted the dose response to the right with an increase of IC50 from 192 mM to 384 mM, but failed to affect maximal inhibition.