Hi, Fabio.

Impossible to stain sciatic nerve, the largest nerve, in the body! Even if you find antibodies marking abundant proteins, ECM or surface proteins, the antibody molecules are too big to access to the node surfaces without appropriate fixation, permeation or teasing the tissues. The nerve bundles consist of a tough cellular organization of many axons, myelinating Schwann cells and fibroblasts, not mentioning tightly accumulated ECM for maintenance of the tissues. You could see staining if you tease the tissues. People found that maturing node is associated with accumulation of mitochodria in node region due to the provision of high energy demand (ATP) for continuous axon potential. Try live staining in teased nerve with Rh123 (MitoTracker), followed by washing with buffer and observe under a fluorescence mike. A very small molecule staining live mitochondria alone.

Best wishes.

Thank you. Teasing would indeed be necessary, I know this. My main concern is not to alter the mechanical properties of the tissue, whilst being able to image nodes of ranvier. I have seen many people imaging various components (Syndecan-3, Gliomedin, CASPR, etc), but always in fixed and permeabilised samples, and I was wondering whether anyone here has worked with a marker that can be stained without pre-processing.

I do not understand what you exactly mean not to alter the mechanical properties - probably to keep it in its natural position. As I know, mcrodisection / dissociation of nerve fibers whch you can make just with a common needle or with special sophisticated devices, in an appropriate solution (e.g. Ringer, maybe Tyrode), keeps the nerve fibers functional for at least half an hour. Anyhow, the isolated fibers will keep their myelin sheath and the nodes berween the segments of myelin. So, you can try to isolate them, and put some drops of the substance you can test on and wait for few minutes while it is trapped by the fibers.

You might attempt to use negative staining for EM, after dispersing the fibers, but you will compromise the electric function, ionic transfer etc