5-HT2 antagonists reduce ON responses in the rabbit retina.

We have investigated the effects of serotonin (5-HT2) antagonists in the rabbit retina. These antagonists reduce the ON responses of ON-center cells as well as the surround (ON) responses of OFF-center cells, and enhance the center (OFF) responses of the latter cells. The result is consistent with the anatomy of the indoleamine-accumulating cells in the rabbit retina, which ramify in sublamina b (ON) of the inner plexiform layer and contact primarily bipolar cells that are depolarizing in the rabbit. This suggests that at least part of the surround (ON) responses to OFF-center cells is generated in the inner plexiform layer.