Luxol fast blue stained sections show dark blue gray matter and lighter blue white matter. This can be most easily corrected by

• A. Continuing the differentiation step
• B. Washing in acidified solution
• C. Increasing stain duration
• D. Using a different fixative

Answer: (A)

In Luxol fast blue staining, myelin-rich white matter should take up the blue dye more intensely than gray matter, which remains lighter because it lacks myelinated fibers. If gray matter appears dark blue, the dye has not yet been adequately removed from nonmyelin tissue. The simplest fix is to continue the differentiation step in the appropriate differentiating solution (for example, a weak acidified alcohol or acetone-based differentiator) until the gray matter lightens while the white matter retains its blue stain. Extending the stain duration would worsen non-specific staining, and changing the fixative won’t resolve the issue once staining has already occurred.