Axotomy, axocompression, axocontusion: effects of mechanical injuries on the catecholamine content of unmyelinated syC fibers.

Authors studied the effects of transection (axotomy) and crush of the rat sciatic nerve, by means of De La Torrés glyoxalic acid fluorescence histochemical technique. It was shown that a simple nerve crush (axocompression) did not induce any major change in the number and fluorescence intensity of unmyelinated axons in the distal stump of the sciatic nerve, even though myelinated axons underwent Wallerian degeneration. By contrast, axotomy resulted in a complete cessation of catecholamine-induced fluorescence; similar effect was exerted by an intense, controlled crush (axocontusion). Supposing that not only postganglionic (syC) but also sensory (drC) unmyelinated axons undergo similar alterations after various mechanical injuries, the apparently controversial results regarding the effects of axotomy and nerve crush, in producing transganglionally mediated depletion of marker substances in the upper dorsal horn, can easily be reconciled.