Inhibitors of phosphorylation of the MEK and the PKA pathways reduce DOM-stimulated CREB phosphorylation. (A) Transient DOM application (2 μM, 24 h) to hippocampal slices significantly enhanced CREB phosphorylation (*P < 0.005 vs. C). (b-d ) Organotypic slices were cultured in the presence of the MEK inhibitor PD98059 (B), the PKA inhibitor H89 (C) or the CaMKII inhibitor KN93 (D) for 1 h, and then treated with 2 μM DOM for 24 h (insult). Lysates were collected at the indicated hours post insult (HPI). Compared to DOM alone, the increased CREB phosphorylation was reduced when DOM was coincubated with PD98059 (B) or H89 (C). However, KN93 did not inhibit the response to DOM (d). The blots correspond to representative experiments and values are the means ± SEM of at least three experiments performed from different cultures (#P < 0.005 vs. -PD98059, H89 or KN93 within the same group; *P < 0.01 vs - PD98059, H89 or KN93 within C group).