Degeneration of the greater splanchnic nerve by operation.

By 1 d after unilateral ligation or severance of the greater splanchnic nerve in the rat immediately caudal to the diaphragm, mitochondrial swelling, lysosomal multiplication and an increase in electron density in axoplasm combined to form a debris of axoplasm in unmyelinated fibers, and both shrinkage and disintegration of myelin occurred in myelinated fibers in the distal stump of the nerve operated upon. By 2 d after operation, the nerve had shrunk to 2 third its original diameter, and most of the nerve fibers except for prominent thick myelinated fibers had dissolved into fatty droplets or other bodies, which were phagocytized by Schwann cells. The degenerated parts adjacent to ligation were then completely replaced by many fibroblasts and numerous collagenous fibers, and the ganglion cells which escaped from direct injury by operation, survived with a remarkable number of free ribosomes and many autophagic lysosomes dispersed within their cytoplasms, together with intact axon terminals, while a few myelinated and several unmyelinated fibers also underwent degeneration at the proximal stumpf of the nerve. These facts can suggest not only that centrifugal elements in the greater splanchnic nerve degenerate more drastically and quickly than has been reported hitherto, but also that there are characteristics of centripetal function in a few myelinated and several unmyelinated fibers.