Springer Online Journal Archives 1860-2000
Summary Propidium iodide, like its analogue ethidium bromide, is a compound which can be used as a marker of nucleic acids. This substance emits a red fluorescent light after exposure to UV light and has therefore been used previously as a nuclear stain in immunofluorescence studies and in flow cytometry. The present experiments were carried out to find out if propidium iodide could be traced in sections of the nervous system after i.v. injections. Due to the general toxicity of the compound detectable amounts of propidium iodide could not be obtained by a single i.v. injection. However, multiple injections of small amounts (0.1 mg) over a period from 15 min to 8 h (total dose 0.7–1.0 mg) were tolerated without any signs of adverse effects. In such experiments propidium iodide did not extravasate inot the cerebral gray or white matter, i.e., areas of the brain located within the blood-brain barrier (BBB). On the other hand, the compound spread into the choroid plexus, the circumventricular organs, the Gasserian ganglion, and sciatic nerve, i.e., regions located outside the BBB. It had a strong tendency to label the nucleus and the perikaryon of the cells in each of these territories. Perifascicular injection of propidium iodide around the sciatic nerve was followed by a marked cellular uptake not only in the epineurium but also in the endoneurium. The shape and position of the labeled nuclei strongly indicated that they were the nuclei of Schwann cells. Previous studies have shown that propidium iodide can be used as a retrograde tracer in neuroanatomic research. The compound, due to its fluorescent properties, appears to be useful for future studies in which one would like to influence the DNA contents in various cell populations of the nervous system. By using the retrograde axonal route groups of neurons could be influenced without causing primary injury to neighboring cells. By using the perifascicular mode of injection, the DNA content of Schwann cell nuclei can be influenced and the resulting effects investigated.
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