[Microglia and pericytes of the human cerebral cortex]

Biopsies of normal human cerebral cortex were fixed by aldehydes and their ultrastructure was studied. Two main types of vessels are observed, capillaries and metarterioles, and around them two types of pericytes are described: a microgliocyte-like pericyte which is either surrounded by a nervous basal membrane, or laying outside this membrane; endothelial-like pericytes which are frequently observed inside the metarterioles perivascular space and contain many lysosomes. Endothelial-like pericytes have probably a metabolic function and microgliocyte-like pericytes are more involved in a role of mechanic regulation of the microcirculation. This hypothesis is supported by the observation of a microgliocyte interposed between two endothelial processes and protuding into the vascular lumen.