Specific uptake of intracranial horseradish peroxidase (HRP) by microglial cells in the goldfish.

Intracranial injections of horseradish peroxidase (HRP) in the goldfish labeled a population of cells with many similarities to microglia. The fact that neither macroglia nor neurons appeared to be labeled by these injections supports this identification. The labeled cells responded to Wallerian degeneration of the optic paths by accumulating in the optic terminal zones, a cellular behavior which strongly supports their identification as microglia.