The ability of selected neurotropic viruses to move transneuronally in the
central nervous system makes them particularly well suited for use as trace
rs in experimental neuroanatomy. Recently, techniques have been developed f
or using rabies virus as a transneuronal tracer. Several features of rabies
infection make the virus particularly useful for this purpose. We examined
transneuronal transport of rabies in the central nervous system of primate
s after intracortical and intramuscular injections. Rabies was transported
in a time-dependent manner to infect synaptically-connected chains of neuro
ns. Transport occurred exclusively in the retrograde direction. At the surv
ival times we used, rabies infection was restricted to neurons and did not
cause cell lysis. There are several methodological and safety issues that m
ust be considered when designing studies that use rabies as a transneuronal
tracer. When appropriate protocols and laboratory practices have been esta
blished, transneuronal transport of rabies can be a safe and efficient tool
for revealing the organization of multi-synaptic circuits in the central n
ervous system. (C) 2000 Published by Elsevier Science B.V.