Activity induced effects. Running is known to enhance proliferation of cells in the dentate gyrus while enriched environment has a stronger effect on neuronal survival. We found that while RUN increased cell proliferation in WT mice, this was not the case in CB1-/- mice. CB1-/- mice showed an increased baseline proliferation (A). In CB1-/- ENR-induced increase in cell survival was abolished. (B) Both housing conditions resulted in an increase of CB1-mRNA in the hippocampus of wild type mice. The early neuronal marker Nestin was only increased in the RUN paradigm (C); * p ≤ 0.05.