Figure 2. Fontana-Masson staining of neuromelanin granules in the substantia nigra and stereological counting of neuromelanin-positive neurons.

(a) Representative sections from rats raised in dim light – dark cycle (left panel) and rats raised in dim light – dark cycle for 70 days and than for 20 days under bright light (right panel). The asterisk on the right panel shows a cell with several tiny granules, while the arrow shows a large granule probably deriving from coalescence of tiny granules. Scale bar: 25 μm. (b) Stereological counting of neuromelanin-positive neurons in the substantia nigra of rats raised in dim light – dark cycle, and rats raised for 20 days or 3 months under bright light. *Significantly different from rats raised in dim light – dark cycle (F_7,7,7 = 51.42870, p = 0.00001, using one way ANOVA plus Scheffe's F test). The three subscript digits adjacent to the F value represent the numbers of rats used for the analysis, sequentially: rats raised in dim light – dark cycle, rats raised for 20 days under bright light and rats raised for 3 months under bright light.