Effects of chemicals on receptors and horizontal cells in the retina

1. By applying atomized chemical solutions on to gecko and carp retinae, neuropharmacological reactions of the photoreceptors and horizontal cells were observed. 2. Sodium L ‐glutamate and L ‐aspartate, glycine, ACh and GABA, had no appreciable effect on the photoreceptor activity. 3. Carp horizontal cells were depolarized by both L ‐glutamate and L ‐aspartate. When maximally depolarized, the action of the endogenous transmitter from the receptor terminals was completely masked, resulting in abolition of the S‐potentials. 4. Responses to red light in both L‐ and C‐type horizontal cells were more strongly affected by aspartate than responses to blue light. 5. Glycine and GABA hyperpolarized the horizontal cells, and the S‐potentials were diminished. 6. ACh had no effect on the activity of the horizontal cells.