A role for 5HT3receptors in visual processing in the mammalian retina

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Abstract
We investigated the role of 5HT3receptors in the mammalian retina using electrophysiological techniques to monitor ganglion cell activity. Activation of 5HT3receptors with the selective agonist 1-phenylbiguanide (PBG) increased the ON responses of ON-center ganglion cells, while decreasing the OFF responses of OFF-center cells. The application of a selective 5HT3antagonist had a reciprocal effect, namely it reduced the center response in ON-center cells and concomitantly increased the center responses in OFF-center cells. Since putative serotoninergic amacrine cells in the retina are connected specifically to the rod bipolar cell, these agents most likely affect the rod bipolar terminal. These data, together with previous studies, suggest that both 5HT2and 5HT3receptors mediate an excitatory influence which serves to facilitate the output from rod bipolar cells, the formerviaa phosphatidyl inositol second-messenger system, and the latterviaa direction channel.