Early changes in the structure of rat sciatic nerves by ligation.

In order to find any morphological changes that might occur in the accumulation of catecholamine synthesizing enzymes following ligation of the sciatic nerve, light and electron microscopic studies were made in segments both proximal and distal to the ligature of the rat sciatic nerve from the initial period up to 4 days. The earliest changes were observed in the larger myelinated nerve fibers at 0.5 and 1.0 mm segments distal and proximal to the ligature, while little if any changes occurred in smaller myelinated nerve fibers. The non-myelinated fibers showed an increased electron density of axons due to the increase in density of the matrix, increased numbers of microtubules and/or microfibriles and of vesicles and vacuoles of varying size in addition to the enlarged size of the axon. These types of changes in the non-myelinated fibers seem to be more marked in the proximal segments, and are probably responsible for the accumulation of axoplasm containing some enzymes.