Rescue of neuronal survival in cortical cultures by Munc18-1 expression. Representative images of cortical synapses from littermate heterozygotes (top), homozygote KOs for Munc18-1 (middle), or Munc18-1 KOs infected with Munc18-1-containing lentivirus (bottom). Cells were maintained in culture for 11 d before being labeled with antibodies against the presynaptic marker synapsin (first column), the neurofilament marker MAP2 (second column), and the nuclear DAPI marker (third column). The last column shows the combined image of the three labeling procedures with colors that match the relevant labels in the other columns. Bars, 20 µm.