In vivo trans-synaptic transfer of WT Tau protein. LVs encoding V5-hTau46WT were bilaterally injected into the CA1 layer (IS; bregma -5.3) of rat brains (n = 3 rats per group). One, three and five months later, the animals were sacrificed, and the whole brains were processed for immunohistochemical analysis using an antibody to total V5-Tau. Sections from the prelimbic or orbital cortex (bregma +4.7), the olfactory bulb (bregma +5.2) and the CA1 (bregma -5.3, IS) are shown. The scale bars are indicated on the figure. These data showed that V5-hTau46WT is transported from primary to secondary neurons in a time-dependent manner.