Dopaminergic Neurons in the Cat Retina

Dopaminergic neurons have been directly visualized in the flat mount cat retina with an immunohistochemical technique that uses antisera directed to the enzyme tyrosine hydroxylase. In a previous study, three specific neuronal populations‐amacrine cells, displaced amacrine (DA) cells, and interplexiform (IP) cells‐were identified on the basis of morphology in the flat mount retina. The present study incorporates three‐dimensional computer reconstructions and differences in the frequency distributions of soma area to support the original cell classification. The three neuronal populations differ in cell numbers and spatial distributions in the retina; quantitative comparison of two cat retinas shows that the total numbers of cells and the spatial distributions of the three cell populations are consistent between retinas. These results suggest that a single neurotransmitter can serve different functions in modifying signals and flow of visual information within the neural networks of the retina.