Contributions of short-wavelength cones to goldfish ganglion cells.

Abstract

There are conflicting reports about the existence and nature of a short-wavelength cone (S-cone) contribution to ganglion cells in the goldfish retina. The present study sought to resolve these discrepancies by examining the S-cone contribution while recording from single ganglion cells in the excised, isolated goldfish retina. The effect of variations in the retinal preparation (gas content and type of background lighting during recording) on the S-cone input was also examined. Cells were classified into one of three types based on the responses at light onset and offset, when responses were driven only by the long-wavelength cone system (L-cones) of the receptive field's center (L+/-(on-excitation/off-inhibition), L-/+, and L+/+). With rare exceptions, the threshold spectral sensitivities of the centers and surrounds of cells that possessed opposite on and off responses (L+/- and L-/+) exhibited S-cone contributions, either prior to and/or during chromatic adaptation of the middle- and long-wavelength cones; the S-cone response was antagonistic to the L-cone input. The L+/+ center cells also contained a S-cone input, but it was synergistic to the L-cone input at suprathreshold intensities. These findings were robust across all of the retinal preparations employed. The discrepancies in the previous work were probably due to the incomplete classification of cells because of the use of threshold responses only.