A technique of silver impregnation for nervous tissues in frozen sections of the human central nervous system with potassium ferricyanide.

A simple and yet reliable technique of silver impregnation for demonstrating nerve fibers in frozen sections of the human central nervous system is described. The following procedure is recommended. Frozen sections 10-25 micrometers thick, 5% aqueous solution of potassium ferricyanide for 2 h (37 degrees C), 10% aqueous solution of silver nitrate for about one h (37 degrees C) or until sections obtain a light brown tint, ammoniacal silver solution, reduction in 20% formalin, gold toning dehydrating and mounting. By this procedure, fine fibers display a color range from purple to dark purple on an almost colorless background. Gold treatment may be omitted. The technique described here is compared and discussed with an earlier technique using potassium ferrocyanide (Ogawa 1979).