List two regressive methods of staining nerve components.

• A. Weil and Luxol fast blue
• B. Bodian and Bielschowsky
• C. Cresyl echt Violet and Bielschowsky
• D. Luxol fast blue and Cresyl echt Violet

Answer: (A)

Regressive staining methods rely on an uptake of stain followed by a differentiation or decolorization step that removes excess dye from non-target tissue, yielding high contrast for the desired nerve components.

Weil's method uses silver impregnation to visualize nerve fibers while background is selectively decolorized, so axons and neurofibrils stand out clearly against a lighter surrounding tissue. Luxol fast blue binds to myelin lipids, and after staining a differentiation step with an acid-alcohol solution removes stain from nonmyelinated tissue, leaving myelin in blue. This combination is classically used to highlight myelinated fiber tracts, with the differentiating step constituting the regressive part.

The other options mix stains that are not both regressive for nerve components (for example, some emphasize cell bodies rather than fibers, or rely on silver methods that aren’t characterized primarily by a differentiation decolorization step).