Scanning electron microscopic study of periendothelial cells of the rat cerebral vessels revealed by a combined method of corrosion casting and KOH digestion.

A combined method of corrosion casting and KOH digestion was used for the scanning electron microscopic (SEM) observation of the external walls of the blood vessels running on the surface and in the parenchyma of the rat cerebral cortex. The plastic resin which was preliminarily injected into the cerebral vessels reinforced the preservation of the vessel walls during the chemical digestion. Using the present method, the walls of blood vessels running on the surface and in the parenchyma of the cerebral cortex were clearly seen with SEM. The arterioles showed a rich arrangement of smooth muscle cells embracing the external surface of the endothelia, and the venules had sparse, flat smooth muscle cells. The capillaries were surrounded by many pericytes which were extremely similar to those seen in the other organs of the animals. There were observed two different kinds of pericyte. One type of the pericytes in the present specimens extended very long cytoplasmic processes parallel to the long axis of the capillaries. Another type of the pericytes had relatively short, broad and flat cytoplasmic processes radiated to embrace the capillary walls. The former was frequently seen in the capillaries on brain surface and in the parenchyma, whereas the latter was relatively rare. The availability of the present method was also discussed in comparison with the previous descriptions.