In a different study, Lopez-Toledano and colleagues (2007) used PDGF-APPswe,Ind mice, similar to Jin and colleagues (2004). In support of the latter Lopez-Toledano et al. observed an increase in proliferation of hippocampal cells, as well as an increase in their neuronal differentiation. This increase was attributed to detectable levels of oligomeric Aβ (Lopez-Toledano and Shelanski, 2007). In contrast, increased proliferation at later time points, close to onset of deposition or post deposition could not be observed (Lopez-Toledano and Shelanski, 2007). The different regimen of BrdU injection (single injection in Lopez-Toledano and colleagues and repetitive dose for consecutive days in the Jin and colleagues and Haughey and colleague studies) makes the comparison between the different observations challenging, particularly if a change in cell cycle takes place in one of the animal models. Similar observations to Jin and colleagues and Toledano-Lopez and colleagues were observed in a separate study using pPDGF-APPSw,Ind (Gan et al., 2008), suggesting an increase in proliferation and differentiation of hippocampal progenitors in these mice at 2 months of age. Interestingly, in contrast to Jin et al. (2004) and
