Figure 1. Modulation of bass horizontal cell HGJ channels by voltage, Ca²⁺ and RA

A: An example of HGJ current in an H-2 type horizontal cell in Ca²⁺ free media (left trace). When the cell was depolarized to 30 mV for 10 s from a holding potential of -60 mV, an outward current slowly activated. Repolarization to -60 mV produced an inward tail current which inactivated. When the cell was exposed to 2 mM Ca²⁺ media, both the outward current and the tail current were inhibited. B: Current-voltage relationship for HGJ channel currents constructed from tail currents induced by voltage clamp steps from 30 mV to -60 mV with 10 mV decrements from a holding potential of 30 mV. Closed squares represent steady state tail currents and closed circles represent peak tail currents. Each point is the mean current from 4 cells. C: RA inhibition of HGJ channel current. 0.3 mM at-RA significantly reduced outward current evoked by stepping to 30 mV in Ca²⁺ free solution. Cell holding potential was -60 mV.