Effect of age and genotype on the number of dopamine neurons in the substantia nigra.

<p>(A–F) Representative coronal sections from <i>Aldh1a1</i>^−/−×<i>Aldh2</i>^−/− mice and age-matched wild type controls showing regions of substantia nigra pars compacta (SNpc) selected for TH+ cell counts. Quantification data of (G) TH+ neurons, (H) Nissl cells, and (I) TH+ cell volume are expressed as the mean ± SEM of the following number of mice in each group: young (wt = 4, ko = 3), middle-aged (wt = 5, ko = 5) and old (wt = 5, ko = 9) male mice. *<i>P<0.05</i>, significantly different from age-matched wild-type control group.