Cytological study of the cellular changes after transection of the proximal radix of the rat trigeminal ganglion.

Cytological changes following transection of the proximal root of the trigeminal ganglion in adult rats were assessed by light and electron microscopy. Radices were transected about 3-5 mm from the ganglia and animals were killed from 1 to 60 days after the operation. Light microscopically, it was found that all Nissl granules became uniformly stained and evenly distributed throughout the cytoplasm within 3 days. Three types of cell alteration involving Nissl granules occurred within 3 to 12 days after the operation: 1) chromatolysis, 2) dark staining of the cytoplasm accompanied by an increase of Nissl granules, and 3) faint staining of the cytoplasm accompanied by dispersion of Nissl granules. Electron microscopically, the chromatolysis pattern was characterized by peripheral concentration of the granular endoplasmic reticulum (gER) and ribosomes in the cytoplasm. Neurons of the dark-staining type showed an increased number of polysomal complexes throughout the cytoplasm, whereas those of the faint-staining type had diffusely dispersed cisternae of the gER which were shortened and bore reduced numbers of attached ribosomes. Perinuclear localization of profiles of Golgi complexes disappeared temporarily 1-3 days after the operation, but the normal perinuclear pattern appeared to return after 1 week. Enzyme histochemistry of acid phosphatase activity revealed an increase in the number of very fine reaction products in the cytoplasm up to 14 days following the operation. Cells recovered the normal pattern of Nissl staining by 48 days. Myelin figures, which are rarely observed in normal ganglia, were still observed in dense lysosomal bodies after 30 days. Nuclear size in affected neurons steadily increased up to about 2 weeks postoperation but returned to normal by 48 days.