Fig. 2.

Effects of DN(PH)-Akt on the nigro-striatal dopaminergic system in normal adult and aged C57BL/6 mice. A: Transduction of the SNpc by intra-nigral injection of AAV DN(PH)-Akt is demonstrated in a representative coronal section of the mesencephalon obtained from a normal adult mouse immunostained for the FLAG epitope at 4 weeks following injection. Brown chromogen deposition is observed throughout the SNpc on the injected experimental side (EXP), but not on the non-injected, control (CON) side (Bar = 250 μm). TH immunostaining of an adjacent section, with thionin counterstain, is shown in the lower panel. The adjacent location of the FLAG- and TH-stained sections is indicated by the similar appearance of distinct landmarks, the fasciculus retroflexus (FR) and the medial terminal nucleus (MT). There is no acute toxicity to the SN, indicated by an intact population of TH-positive neurons in the SNpc on the injected (EXP) side and confirmed by stereologic counts (TABLE). B: At 7 weeks following injection of an aged mouse, DN(PH)-Akt has no effect on the number of TH-positive dopaminergic neurons in the SN, determined by stereologic counts (upper left graph; bars depict the mean ± standard error of the mean in each graph), in comparison to AAV GFP-injected controls (n = 5, both groups). DN(PH)-Akt does, however, have a small (9%) but significant effect on TH-positive neuron size (n = 50 neurons, each experimental condition; p = 0.002, ANOVA; Tukey post hoc analysis as shown) (upper right graph). At 7 weeks following injection, DN(PH)-Akt has a tendency to decrease the density of TH-immunoperoxidase staining of the whole striatum that is not quite significant (p = 0.052, t-test). However, a significant effect is observed in the dorsolateral region of the striatum, where the density of TH immunostaining is reduced by 17% (n = 5 AAV-GFP, 9 AAV DN(PH)-Akt; p = 0.008, t-test) (lower right graph).