4.

Effects of inhibitors of PKA and MAPK on the neurite outgrowth of AMP N₁-oxide-treated PC12 cells (A) and on suppression of growth of PC12 cells elicited by AMP N₁-oxide (B). The cells were precultured for 30 min in medium containing KT5720 (2 μM) or PD98059 (100 μM). Then, AMP N₁-oxide (20 or 100 μM) was added, and the cells were cultured for another 1 day. A: the number of process-bearing cells was counted, and the ratio of them to total cells was calculated. The values are expressed as the mean ± standard error (n = 6). Significant difference from the non-treated cells was determined by one-way ANOVA with Tukey's test, *P < 0.05. ‘ns’ means non-significant relationship. B: the cells were cultured for 4 days in medium containing the indicated concentrations of AMP N₁-oxide and KT5720. The number of cells was then counted, and the values expressed as the mean ± standard error (n = 3). Significant differences from the values of the corresponding cells untreated with the inhibitor were determined by one-way ANOVA with Tukey's test, ***P < 0.001, **P < 0.01, *P < 0.05. Significance of differences in values between non-treated control cells and the cells treated with 20 μM AMP N₁-oxide was determined by Student's t-test, ***P < 0.001.