Tracing of fluoro‐gold prelabeled microglia injected into the adult rat brain

Abstract

In light of a recent interest in the transplantation of cultured microglial cells, we have examined the use of the fluorescent dye Fluoro-Gold (FG) as a tracer for these cells. Following injection into the adult rat brain, FG prelabeled microglial cells were readily traceable for up to 2 weeks with minimal labeling of endogenous cell populations. Some of the injected cells differentiated into ramified microglial cells as a result of exposure to the adult CNS environment. Injection of free FG into the adult rat brain resulted in the widespread labeling of neurons and perivascular cells, but not endogenous microglial cells, indicating that perivascular cells, but not resting microglia, are actively pinocytotic cells of the CNS. Our results show that FG is an effective label for the tracing of transplanted microglial cells. GLIA 23:84–88, 1998. © 1998 Wiley-Liss, Inc.