Retinal Neurochemistry

The vertebrate retina is a complex neural tissue composed of a repeating array of distinct cell types that communicate through specialized synaptic connections. The neurochemistry underlying these connections reveals the synaptic chemistry, including the neurotransmitters involved and their corresponding receptors. The basic pattern of communication is that the pathway from photoreceptors to bipolar cells to ganglion cells typically uses glutamate as the signaling transmitter, with three ionotropic and one metabotropic receptor types. In contrast, much of the lateral feedback, performed by horizontal cells and amacrine cells, uses the inhibitory neurotransmitter GABA, while other amacrine cells use glycine or dopamine. This review examines all of these neurotransmitter systems for each retinal cell type, along with how these systems process the visual signals transmitted to the lateral geniculate nucleus and the visual cortex.