We have constructed a deletion-mutant rabies virus encoding EGFP and find it to be an
excellent tool for studying detailed morphology and physiology of neurons projecting to
injection sites within the mammalian brain. The virus cannot spread beyond initially infected
cells yet, unlike other viral vectors, replicates its core within them. The cells therefore
fluoresce intensely, revealing fine dendritic and axonal structure with no background from
partially or faintly labeled cells.