Answer: The Luxol fast blue stain, or LFB stain, is an anatomical analysis technique that is used to identify myelin in the brain.
One reason scientists use the Luxol fast blue stain is to differentiate white matter from gray matter in sections of brain tissue. Being able to identify the two is advantageous from a neuroanatomical perspective since white matter and gray matter have unique properties, and knowing the difference allows us to infer some information about the functions of the regions in a brain slice. Also, neuroanatomists often use paths of white matter, such as the corpus callosum, as a landmark for identifying regions of the brain.
White matter itself appears white because of a layer of myelin that surrounds the axons. Myelin is a cellular modification to the axons of neurons. A neuron that has been myelinated is able to send action potentials down the axon more rapidly than one that is not myelinated. Gray matter, on the other hand, is mostly cell bodies of neurons, which are usually unmyelinated.
The Luxol fast blue stain is able to target lipoproteins, which are abundant in myelin sheaths. As the name indicates, myelin comes out as blue. The stain also causes discoloration of other parts of the nervous tissue, as the neuropil (including unmyelinated axons and dendrites) comes up as pink, while cell bodies stain as purple. Chemically, LFB is a copper based dye. It usually requires a long overnight period of exposure before tissue takes up the Luxol stain.
There are many advantages to identifying changes in myelination in the brain. One way to assess myelination status is to work with a stain that is able to identify myelin.
Myelin can be lost in a variety of conditions or disease states. For example, multiple sclerosis (MS) is a common neurological condition resulting in a dysfunctional immune system-mediated loss of myelin, which causes symptoms such as muscle weakness, paresthesias, and fatigue. Traumatic brain injury, such as a concussion, can also lead to demyelination (Inflammation and white matter degeneration persist for years after a single traumatic brain injury). Using a LFB stain will be useful here to assess the severity of myelin loss.