(A, B) Voltage steps (top) and resulting exemplar current responses (bottom) for RO cones (black, A) or macaque foveal cones (magenta, B). (C) Current voltage curve at plateau amplitude for RO cones (black, n=15) or primate foveal cones (magenta, n=9). (D–F) Whole cell voltage clamp recording from an individual RO cone, showing leak-subtracted HCN currents (bottom traces) in response to four hyperpolarization steps (top traces) from a holding potential of −50 mV (10 mV increase per step). (D) response before drug treatment (E) after application of 1 mM CsCl. (F) Response after wash-out of 1 mM CsCl. (G) Current voltage curve at plateau amplitude for (D–F). (H) Average measured membrane capacitance of RO cones (37.9 ± 4.6 pF, n=15) or macaque foveal cones (38.1 ± 3.8 pF, n=7). (I) Average measured membrane time constant for RO cones (1.62 ± 0.1 s, n=14) or primate foveal cones (1.1 ± 0.1 s, n=8). (J) Measured average input resistance for RO cones (35.1 ± 2.1 MΩ, n=10) or primate foveal cones (30.9 ± 2 MΩ, n=8). (K) Average measured resting membrane potential for RO cones (−34 ± 2.8 mV, n=19) or primate foveal cones (−51.5 ± 2.7 mV, n=9).