Ultrastructural study of pericytes in the rat supraoptic nucleus

Pericytes of the supraoptic nucleus of normal rats have been studied with the electron microscope. These cells are morphologically similar to those of pericytes in other parts of the nervous system. The pericytes and their cytoplasmic processes were surrounded by basal membrane. The nucleus contained large masses of heterochromatin. The cytoplasm, less dense than that of the endothelial cells, contained numerous free ribosomes, cisternae of granular endoplasmic reticulum, various dictyosomes of the Golgi complex, isolated microtubules, a few mitochondria, and, occasionally, a diplosome. The presence of numerous lysosomes in some pericytes suggested that the cells are phagocytic even in normal circumstances.