DARK-ADAPTATION OF HORIZONTAL CELLS IN THE TELEOST FISH RETINA

The dark adaptation behaviors of rod-driven and cone-driven horizontal cells were examined by analyzing their light responses recorded intracellularly in the intact, immobilized carp, the compared with that of the electroretinographic b-wave recorded simultaneously. Like the b-wave, the light responsiveness of rod horizontal cells increased gradually with time in the dark and attained a steady level at 60 min. On the other hand, cone horizontal cells initially increased in light responsiveness in the first 10 min, but thereafter decreased steadily so that the response amplitudes of these cells to bright light flashes were only 3-5 mV. The results suggest that cone horizontal cells are strongly suppressed in prolonged darkness.