Figure 3. Increased circulating current, faster flash response kinetics, and reduced sensitivity in rods recorded with OS-in on treatment with 50 mM bicarbonate. A, Rod attached to a clump consisting of a cone and five other cells. Flash strengths were: 0.32, 4.8, 17.1, and 72.4 photons μm−2 at 520 nm in MOPS (left), 0.32, 0.59, 4.8, 17.1, 72.4, and 258 photons μm−2 at 520 nm in bicarbonate (middle) and 0.59, 4.8, 17.1, and 72.4 photons μm−2 at 520 nm in the MOPS wash (right). A brighter flash of 258 photons μm−2 was necessary to obtain the saturating response during bicarbonate treatment (middle panel). B, Isolated rod that retained its spherule. Flash strengths were: 1.0, 2.4, 8.1, 36.2, and 124 photons μm−2 at 500 nm in MOPS (left, right) and 2.4, 8.1, 36.2, 124, and 239 photons μm−2 at 500 nm in bicarbonate (middle). C, Faster flash response recovery with bicarbonate for the isolated rod in B. Dim flash responses, whose peak amplitudes were less than a fifth of the maximum, were scaled to their peak amplitudes. Integration time, given as the integrated area of the normalized dim flash response, decreased ∼16% with bicarbonate. D, Loss in sensitivity to flashes of the rod in B with bicarbonate. Results were fit with a saturating exponential function: r/rmax = 1 – exp(-ki) where k is a constant equal to ln(2)/i0.5 and i0.5 is the flash strength eliciting a half-maximal response.