MEK/ERK signaling mediated the synaptic modification by SPN-associated PP1. a, Effects of MEK inhibitor U-0126 on NMDAR-EPSC amplitudes in neurons expressing SPN(WT) or SPN(F451A). The horizontal bar indicated the period of extracellular U-0126 perfusion. n = 6 neurons in each group. b, MLC phosphorylation (pMLC) significantly increased at day 3 after SPN(F451A) expression, which, however, could be repressed by spinal treatment with U-0126 (5 μg) or MLCK inhibitor ML-7 (50 μg) for 30 min. *p < 0.05 relative to GFP rats, #p < 0.05 relative to SPN(F451A) rats. n = 6 experiments. c, Postsynaptic loading of ML-7 through the recording pipettes inhibited NMDAR EPSCs in neurons expressing SPN(F451A). n = 6 neurons in each group.