Figure 5. Diminished enteric neurons in the colon of old mice. PGP9.5 recognized perikarya and nerve fibers within MP, and PGP9.5-positive area per field in 20-mo-old mice were significantly declined compared with 2- and 16-mo-old mice (A-B). The reduction in protein expression of PGP9.5 (C) and HuC/D (D) was observed in aging mice consistent with morphological results. Densitometric analysis of protein expressions normalized to α-Tubulin. Statistical analysis was performed using one-way analysis of variance and data were represented as mean ± SD, statistical significance is: (B-D) ## P < 0.01, ### P < 0.001 compared with 2-mo-old group; ** P < 0.01, *** P < 0.001 compared with 16-mo-old group; n=5 mice per group. Abbreviation: Co, colon.