Preparation and composition of the synaptosome. (A) Schematic representation of a synapse, indicating where the presynaptic nerve terminal (upper dotted line) and attached postsynaptic density (lower dotted line) pinch off following homogenization of brain tissue to form a synaptosome. (B) Labels indicate synaptic vesicles (SV), mitochondria (mito), and the postsynaptic density (PSD). (C) An electron micrograph of a rat brain synaptosome, illustrating the features in B. Scale bar, 100 nm. (Micrograph courtesy of Professor M.A. Cousin, University of Edinburgh.)