Six weeks after discontinuation of a 28 day GCV infusion, both proliferation and neurogenesis recover in the DG contralateral to the site of GCV infusion. A–B: Mcm2-immunoreactive, proliferating cells are found only contralateral (C in lower left) to the side of GCV infusion in the DG of a nestin-tk+ (tk+) animal (B) as opposed to bilaterally in a wild-type (wt) control (A). C–E: Immature neurons immunolabeled for DCx are present contralateral (C in lower left) but not ipsilateral (I in lower left) to the side of GCV infusion in this tk+ mouse (D), although more immature neurons are apparent in the wt control (C, E). GCL, granule cell layer; H, hilus; ML, molecular layer. Scale bars = 50 μm (A–B), 100 μm (C–D).