Figure 5.

The PCP2-null rod bipolar cell has a larger light response and a more depolarized resting membrane potential than the wild-type cell. Whole-cell recordings from rod bipolar cells in WT and null (KO) mice were performed in current-clamp (CC) (A, C, D) and voltage-clamp (VC) modes (B, E, F). Holding potential was −60 mV. The image located between A and B shows a typical retinal slice with a Lucifer yellow-stained rod bipolar cell (b) and an attached recording electrode (e). A, B, Voltage and current responses of a single rod bipolar cell to 10 ms flashes (dotted lines) of increasing intensities. Intensities given in log photons μm⁻² are shown by the numbers below the traces. C, E, Average voltage and current responses to a saturating flash intensity of 2.9 log photons μm⁻². The average resting membrane potential of the null cells was ∼9 mV more depolarized than that of the wild type, and the holding current of the null cells was ∼20 pA larger than that of wild type (p < 0.001). In C–F, data are from eight PCP2-null mice (40 cells for CC; 43 for VC) and seven wild-type mice (40 cells for CC; 41 for VC). D, F, Intensity–response profiles. At most intensities, the peak voltage amplitude, measured as the difference between baseline and the peak of the response, appeared similar for null and wild-type cells. At the lowest intensity, the null cells did have slightly larger peaks. Under voltage clamp, at all intensities, the peak current amplitude tended to be larger in null than in wild-type cells. Error bars indicate SEM.