Characterization of transsynaptic tracing with central application of pseudorabies virus

Although transsynaptic tracing with peripheral injection of pseudorabies vi rus (PRV) has been extensively characterized, several methodological issues related to central application of this tracer have nor been addressed. Tn the present study, we addressed the following three issues by using microin jection of a cocktail containing PRV (Bartha strain) and cholera toxin subu nit B (CTb) into different sites in the rat brain. First, we estimated PRV diffusion by examining injection sites at different times after application . Second, we tested whether PRV is taken up by fibers of passage following injections into the olivocerebellar pathway. Third, we developed criteria f or leakage of PRV into cerebral ventricles. Our data indicate that (i) cent rally injected PRV diffuses very little and produces focal injection sites; (ii) PRV is taken up and transported by fibers of passage, although less p rominently than found for Ctb; (iii) PRV produces specific and easily ident ifiable ependymal cell as well as neuronal labeling following ventricular i njection. This labeling can be used as a criterion for determining if label ing obtained was due to injected tracer leaking into brain ventricles. In s ummary, the present study provides neu and important information about usin g PRV to trace central multisynaptic circuitry. (C) 1999 Elsevier Science B .V. All rights reserved.