AbstractThrough the application of combined neurochemical and anatomical techniques it has been possible to assign putative neurotransmitter substances to several neuron classes in the goldfish retina. Rod photoreceptors appear to use glutamic acid or a close analog as their transmitter substance. Red‐sensitive and green‐sensitive cones appear to use some acidic amino acid or close analog, but neither aspartic nor glutamic acid appears to be a reasonable candidate. At present, blue‐sensitive cones have not been assigned a plausible neurotransmitter substance. Horizontal cells, known as type H1, use gamma‐aminobutyric acid (hereafter abbreviated GABA). A type of pyriform amacrine cell whose dendritic processes branch in the deepest part of the inner plexiform layer also uses GABA. A large population of small‐bodied amacrine cells with diffuse dendritic arbors branching in the middle of the inner plexiform layer utilize glycine. One type of indol‐amine‐accumulating amacrine cell is found to branch in the most superficial portion of the innerplexiform layer. Two classes of interplexiform cells have now been characterized: One employs dopamine and the other uses glycine. The majority of the retinal channels modulated by these conventional transmitter substances are dominated by red‐sensiti
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