The alteration of intracellular pathways induced by ERK pathway inhibition is Ca²⁺ influx dependent. A–D, Western blot analysis and quantification of SMN protein expression in control (A, B) and SMA (C, D) spinal cord explants in the presence or absence of U0126 or the calcium chelators EGTA and BAPTA-AM (n = 3). E–H, Western blot analysis and quantification of CaMKII protein phosphorylation in control (E, F) and SMA (G, H) spinal cord explants in the presence or absence of U0126 or either the calcium chelators EGTA and BAPTA-AM (n = 3). I–L, Western blot analysis and quantification of CREB protein phosphorylation in control (I, J) and SMA (K, L) spinal cord explants in the presence or absence of U0126 or either the calcium chelators EGTA and BAPTA-AM (n = 3). M, Time course of the U0126 effect on an Oregon Green 488 BAPTA-1-loaded motor neurons recorded in spinal cord section of a control mouse. Images represent either the basal fluorescence level (left side) or the fluorescence at the peak of the response (right side). Scale bars, 20 μm. Inset shows spikes recorded on the same cell under the cell-attached configuration of the patch clamp. Data are displayed as mean ± SEM. *p < 0.05.