Selective Silver Impregnation of Degenerating Axons in the Central Nervous System

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Rat and rabbit brains containing surgical lesions of 5–10 days’ duration were fixed in 10% formalin (neutralized with calcium carbonate) for 1 week to 6 months. Frozen sections (15–20μ) were rinsed and then soaked 7 minutes in a 1.7% solution of strong ammonia in distilled water. Subsequent treatment was as follows: rinse; 0.05% aqueous potassium permanganate 5–15 minutes; 0.5% aqueous potassium metabisulfite, 2 changes of 2.5 minutes each; wash thoroughly in 3 changes distilled water; 1.5% aqueous silver nitrate, 0.5–1.0 hr.; 1% citric acid, 5–10 sec.; 2 changes distilled water; 1% sodium thiosulfate, 30 sec.; 3 changes distilled water. Each section is then processed separately. Ammoniacal silver solution (450 mg. silver nitrate in 10 ml. distilled water; add 5 ml. ethanol; let cool to room temperature; add Í ml. strong ammonia water and 0.9 ml. of 2.5% aqueous sodium hydroxide), 0.5–1.0 min. with gentle agitation. Reduction of about 1 minute is accomplished in: distilled water, 45 ml.; ethanol, 5 ml.; 10% formalin, 1.5 ml.; 1% citric acid, 1.5 ml. Rinsing; 1% sodium thiosulfate, 10 sec.; thorough washing followed by dehydration through graded alcohol and 3 changes of xylene or toluene complete the staining process. Normal nerve fibers are slightly stained to unstained, degenerating fibers, black. The treatment in potassium permanganate is critical since too little favors overstaining of normal fibers and too much abolishes staining of degenerating fibers.KeywordsPotassium PermanganateSodium Thiosulfate SolutionWalter Reed Army MedicalTerminal DegenerationAmmoniacal SilverThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.