The experiments described in this proposal are designed to investigate two related problems: i. the functional specificity of amacrine cells as internuncial neurons in the retina, and in particular, their neurotransmitter-related functional specificity, and ii. the charactrization of retinal ganglion cells, relating their neurotransmitter-specific synaptic inputs to their form and function. Of primary interest are the neuronal architecture and synaptic relationships involving """"""""starburst""""""""/cholinergic amacrine cells, GABAergic amacrine cells, and three types of ganglion cell: X cells, Y cells, and directionally selective (DS) ganglion cells, the physiology of which is significantly shaped by these two kinds of amacrine cell. Further studies are aimed at understanding the developmental sequence of synapse formation between these amacrine and ganglion cells, as it relates to the emergence of functional properties, and the specificity of neuronal connections in the retina. Experiments are designed to make physiological identification of X, Y, and DS ganglion cells in an in vitro preparation of rabbit retina, and to stain them during intracellular recording with horseradish peroxidase (HRP). The morphology of HRP-stained cells is to be studied by light microscopy (LM) and computer graphic analysis, compared with a large sample of Golgi-impregnated ganglion cells, and their synaptic inputs studied by electron microscopy. Double labelling studies will show the synaptic relationships between starburst amacrine cells, GABAergic amacrine cells, and the three types of ganglion cells cited above. EM autoradiography will be performed on retinas incubated with (3H)GABA, and impregnanted by the Golgi method to produce labelling of GABAergic synapses in the vicinity of Golgi-labelled starburst/ACh amacrine cells. Identified X, Y, and DS ganglion cells will also be included in this study. At a later state, EM studies of developing neurotransmitter-specific connections will be performed, as well as studies in the in vitro preparation of the physiological development of the five types of neuron now being studied in the adult. This work examines visual mechanisms served by specific neurotransmitters, so that when it is appropriate to apply drug treatments to the eye, influencing retinal neurotransmission, a detailed understanding of the normal visual processes affected will be established. The developmental studies will provide a basis in fundamental research for understanding how neurotransmitter-related genetic disorders will affect vision.
