Certain retinal horizontal cells have a center-surround antagonistic organization

Retinal horizontal cells form a broad receptive field, which contributes to generating antagonistic surround responses in retinal bipolar cells. Here, I report that certain horizontal cells themselves have center-surround antagonistic receptive fields. The receptive fields of yellow/red, blue-type horizontal cells (Y/RB HCs) in the carp retina were measured by the response to the slit of light stimulus using the conventional intracellular electrode. A center stimulus of monochromatic light of 500 nm hyperpolarized Y/RB HCs, whereas the peripheral light depolarized the cells, suggesting that these cells exhibit an antagonistic receptive field at 500 nm light. The length constant of Y/RB HC's depolarizing responses to 600 nm light was 1.22 +/- 0.08 mm, which was larger than that (0.61 +/- 0.06 mm) of hyperpolarizing responses to 500 nm light. Thus, depolarizing responses of Y/RB HCs exhibit a larger receptive field than hyperpolarizing responses. The length constant of hyperpolarizing responses of luminosity-type HCs (LHCs) was 1.19 +/- 0.07 mm, which was similar to that of 500 nm depolarizing responses of Y/RB HCs (1.34 +/- 0.11 mm). Depolarizing response of Y/RB HCs was decreased by bath application of GABA and picrotoxin, a GABA receptor antagonist, suggesting that GABAergic signaling may modulate center-surround antagonistic mechanisms in Y/RB HCs. Bipolar cells display center-surround antagonistic receptive fields that play important roles to improve visual contrast. Wide receptive fields of HCs contribute to generating surround responses in bipolar cells. Therefore, the response polarity of Y/RB HCs may affect the width of the surround receptive field in bipolar cells. NEW & NOTEWORTHY Retinal horizontal cells form a broad receptive field, which contributes to generating antagonistic surround responses in retinal bipolar cells. Here, I found that depolarizing responses of yellow/red, blue-type horizontal cells (Y/RB HCs) exhibit a larger receptive field than hyperpolarizing responses at monochromatic lights between 480 nm and 520 nm. Because bipolar cells play a key role in the detection of visual contrast, depolarization or hyperpolarization of Y/RB HCs may regulate the size of the surround receptive field in the bipolar cells.

Automated summary

Retinal horizontal cells have broad receptive fields that contribute to generating antagonistic surround responses in retinal bipolar cells. This study found that depolarizing responses of yellow/red, blue-type horizontal cells exhibit a larger receptive field than hyperpolarizing responses at monochromatic lights between 480 nm and 520 nm. The depolarization or hyperpolarization of these cells may regulate the size of the surround receptive field in bipolar cells, which play a key role in visual contrast detection.