A histochemical and electron-microscopic study of the trigeminal ganglion of the rat

Abstract

The electron-microscopic and the enzyme histochemical studies were carried out and the following findings obtained: 1. (1) Light-microscopically, three types of the nerve cells were distinguished, i.e., large cells, small cells and intermediate cells. Electron-microscopically, three types of cells were also discernible, i.e., clear cells, dark cells and transitional cells. The diameter of large cells was about 60 μ and that of dark cells, 30 μ. The mitochondrial dehydrogenases were more evident in the nerve cell bodies than in capsular cells. Mitochondria were more numerous in nerve cell bodies than in capsular cells. In dark cells, the mitochondrial dehydrogenases were concentrated in the perinuclear area and AChE was mainly localized in the peripheral portion of the perikaryon. In large cells, these enzymes were distributed throughout the perikaryon. The intracellular localization of the enzymes were coincident with the intracellular distributions of the mitochondria and the rough surfaced endoplasmic reticulum in the perikaryon of the aforementioned nerve cell types. Therefore, it was suggested that the large cell was identical with the clear cell, the small cell with the dark cell and the intermediate cell with the transitional cell. 2. (2) The capsular and/or the Schwann cell intervened between the neuron and capillary vessels. 3. (3) The capsular cell showed the characteristically prominent stainability to NADP-dependent IDH, G6PDH and to ALP. Electron-microscopically, the two types of the capsular cells were discernible, i.e., dark capsular cells and clear capsular cells. At the junction of clear cells and capsular cells there were “labyrinthine structures” and “trophospongium” and these structures may play a role in the transportation of nutrition between the two cells. On the other hand, no such structure was observed in dark cells. 4. (4) It is reasonable to assume that there is transformation of the nerve cell types in various biological states from dark cell to clear cell.