The Journal of Neurophysiology Vol. 77 No. 1 January 1997, pp. 511-516
Copyright ©1997 The American Physiological Society

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An In Vitro Model of the Kitten Retinogeniculate Pathway

William Guido, Fu-Sun Lo, and Reha S. Erzurumlu

Department of Anatomy and Neuroscience Center of Excellence, Louisiana State University Medical Center, New Orleans, Louisiana 70112

Guido, William, Fu-Sun Lo, and Reha S. Erzurumlu. An in vitro model of the kitten retinogeniculate pathway. J. Neurophysiol. 77: 511-516, 1997. An organotypic explant coculture method is described for the developing retinogeniculate pathway of the cat. Retinal explants and thalamic slices containing the dorsal lateral geniculate nucleus (LGN), derived from early postnatal kittens, can be grown in serum-free culture medium for several days. In such cultures, retinal ganglion cells (RGCs) and LGN neurons retained their age-specific morphological features and developed functional connections. Labeling of RGCs and their processes with DiI showed that all three major classes of RGCs (/Y, /X, /W) were present in cocultured retinal explants. Retinal axons readily regenerated into thalamic slices and, over time, developed arbors within the LGN. Retrograde labeling from the LGN traced the origin of these axons almost exclusively to -cells in the retina. In vitro intracellular recordings indicated that LGN cells maintained their basic electrophysiological properties in coculture. Current injection generated action potentials, and, at hyperpolarized levels, it led to low-threshold Ca²⁺ spiking. Regenerated retinal axons also formed functional connections with LGN neurons. Electrical stimulation of the retinal explant elicited excitatory postsynaptic responses (EPSPs) in LGN cells. Drop application of specific glutamate antagonists indicated that EPSPs had both N-methyl-D-aspartate (NMDA) and non-NMDA receptor components. The morphology of the LGN neurons was examined after intracellular injections of biocytin during recording. Labeled cells were very similar to those of early postnatal kittens. Although, in general, they had relatively small soma and simple dendritic branching patterns, a few could be recognized as X- or Y-cells. Thus the coculture model can be used to assay the regenerative propensity of different types of RGCs during development.

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