Mouse cone photoresponses obtained with electroretinogram from the isolated retina

We characterize the dark-adapted photoresponses from mouse cones intact in the isolated retina, their virtually natural environment, by isolating pharmacologically the photoreceptor light responses from the electroretinogram (ERG). Due to the different photoresponse kinetics and sensitivity of rods and cones, the cone responses were readily attained by using a rod-saturating preflash. The stimulus wavelength (544 nm) was chosen to selectively stimulate the green sensitive (“M”-)pigment. Obtained responses were monophasic, showing fast kinetics (mean tp = 51 ms) and low sensitivity (fractional single-photon response ca. 0.23%). The amplification coefficient of cones (4.6 s−2) was very close to that of rods (5.6 s−2), while the dominant time constant of recovery was clearly smaller for cones (33 ms) than for rods (160 ms).