Visualization of human choroidal ganglion cells with the supravital fluorescent dye 4-(4-diethylaminostyryl)-N-methylpyridium iodide.

The distribution and morphology of ganglion cell bodies and nerve fibers in supravital human choroidea is studied by staining with the fluorescent dye 4-(4-diethylaminostyryl)-N-methylpyridium iodide (4-Di-2-ASP). We have used the choroids from human donor eyes donated for cornea transplantation. The isolated tissues were rinsed in ringer solution and processed within up to 24 h after death with 3 microM of 4-Di-2-ASP in Ringer for 5-60 min at different temperatures (4-37 degrees C). After incubation, choroid whole flat mounts were observed in a fluorescence microscope. A delicate network of nerve fibers could be distinguished as soon as 5 min after immersion in 4-Di-2-ASP. In addition, labelled ganglion cell perikarya could be seen after longer incubation periods. They occurred individually or grouped in small ganglia of up to 8 cells and were linked together by various processes, which could also be traced to blood vessels. The fluorescent dye 4-Di-2-ASP provides a quick and simple method to visualize the innervation of the human choroid, including local ganglion cells. This nontoxic fluorescent technique will permit further manipulation and electrophysiological investigation of choroidal innervation.