SNPH is required to arrest axonal mitochondrial movement in response to synaptic activity. (A and B) Kymographs (A) and quantitative analysis (B) showing the motility of axonal mitochondria in snph^+/+ and snph^−/− hippocampal neurons before and after 100-Hz field stimulation in the presence or absence of 1.2 mM CaCl₂ or 1 µm TTX. Neurons were transfected with DsRed-Mito at DIV9 followed by time-lapse imaging at DIV12. Vertical lines in kymographs represent stationary mitochondria; slanted lines or curves to the right (negative slope) represent retrograde movement (also see Videos 4 and 5). Data were quantified from numbers of neurons indicated within bars in three independent experiments. Bars, 10 µm. Error bars show SEM. Student’s t test.