Fig. 1.5.19. Axon (ax) forming two neighboring en passant boutons synapsing with dendritic spines (asterisks). Note how synaptic vesicles accumulate by the region occupied with microtubules and a mitochondrion. D - dendrites, arrow - tangentionally sectioned synapse on the top of dendritic spine. Scale = 500 nm. (Rat, hippocampus.)