Cryo-ET of distinct stages of vesicles in excitatory synapse, inhibitory synapse, synaptic protein – like particles, and PSD densities. (A–C) Synaptic vesicles at different stages of exocytosis show potential release sites on the presynaptic membrane in excitatory synapses. (D) The tomogram slice shows a typical inhibitory synapse with thin PSD. Red Arrows in the inset indicate the PSD. (E–G) Tomographic slices show postsynaptic membrane particles (E), adhesion molecule–like particles (F), and synaptic vesicle–associated particles (G), as arrowheads indicate in synaptosomes. (H) Synaptosomes with separate PSD density clusters. (I) Synaptosomes with separate and continuous PSD densities. (J) Synaptosomes with continuous PSD densities. Arrows indicate PSD density clusters. Scale bars: (A–C) left panels, 50 nm; right panels, 20 nm; (D) left panel, 200 nm; right panel, 200 nm; inset, 50 nm; (E–G) 50 nm; (H–J) 100 nm.