(A-C) Reduced immuno-reactivity of S270 phosphorylated gephyrin but not total gephyrin levels after 4-AP treatment, revealed by conventional fluorescence microscopy (KS test, p < 0.001 in B1 and p < 0.0001 in B2, p < 0.0001 in C). Total gephyrin was probed with polyclonal rabbit primary antibody (rbGPHN), and pS270 phosphorylated gephyrin with monoclonal mouse primary antibody (m7a). Number of synapses: n = 4040 in TTX and n = 3818 in 4-AP conditions from two independent experiments. Scale bar: 2 µm. 