Dependency of agonist-stimulated CREB phosphorylation on ERK activity in SH-SY5Y cells. Time-courses of ERK1/2 phosphorylation stimulated by MCh (1 μM; A) or bradykinin (300 nM; B). Representative immunoblots for phospho-ERK1/2 and total ERK1/2 are shown beneath each histogram. Statistically significant increases in ERK1/2 phosphorylation are indicated as *p < 0.05, **p < 0.01. The effects of the MEK1/2 inhibitor U0126 (10 μM, 30 min pre-treatment) on MCh (1 μM; at 1 and 5 min; C) or bradykinin (300 nM; at 1 and 5 min; D) stimulated increases in phospho-CREB immunoreactivity. Representative immunoblots for phospho-CREB, total CREB and phospho-ERK1/2 are shown beneath each histogram. Data, normalized to the forskolin/IBMX response (=100%) in the absence of inhibitor, are shown as means ± S.E.M. for at least 3 independent experiments. Statistically significant effects of U0126 on CREB phosphorylation are indicated as *p < 0.05, ***p < 0.001.