Effects of the cannabinoid HU210 on PI3K/Akt and ERK signaling in cultured hippocampal NS/PCs. (A) There was no significant change in pAkt or actin in NS/PCs within the first hour after addition of 100 nM of HU210 to culture medium. (B) Application of 100 nM of HU210 rapidly induced phosphorylation of pERK1/2 in NS/PCs in the presence of bFGF and EGF in culture medium. (C) Application of 100 nM of HU210 3 hours after removal of bFGF and EGF from culture medium also induced phosphorylation of pERK1/2 in NS/PCs. (D) Application of the ERK signaling inhibitor U0126 blocked the promoting effects of 100 nM of HU210 on phosphorylation of pERK1/2 in NS/PCs 5 minutes after addition of HU210 to culture medium. (E) Addition of U0126 (10 μM) to the culture medium 1 hour before HU210 antagonized the promoting effects of 10 nM to 1 μM of HU210 on NS/PC proliferation. Error bars represent SEM. *P < 0.05 and **P < 0.01 by Tukey post-hoc tests after 1-way ANOVA. tERK1/2, total ERK1/2.