FIGURE 6.

NMDA prefers to activate p38 MAPK in mature neurons, whereas it favors ERK1/2 activation in immature neurons. On different days in vitro, neurons were starved for 6 h in DMEM without any supplement and then stimulated with the indicated concentrations of NMDA or not in Locke's solution for 15 min. Whole-cell lysates were harvested, and immunoblotting was done by using of anti-phosphorylated p38 or ERK1/2 antibodies (p-p38, t-ERK1/2) and anti-total p38 or ERK1/2 (t-p38, p-ERK1/2) antibodies, with the latter serving as an internal control for protein loading to assess the activation level of p38 and ERK1/2. A, representative blots from 4 independent experiments. B, scanning densitometry was quantified and normalized to sham treatment values on the same blots. *, p < 0.05; ***, p < 0.001 versus control (0). Note the dramatic activation of p38 in 9- and 12DIV neurons but not in 3- and 6DIV neurons, and the strong activation of ERK1/2 in 3- and 6DIV neurons, which becomes rather weak in 9- and 12DIV neurons.