Fig. 1.6.07. Two axo-dendritic synapses on a dendritic shaft (D). The asymmetrical (Gray I) type with spherical synaptic vesicles in the presynaptic bouton and prominent postsynaptic density (S, red asterisk) on the right, the symmetrical (Gray II) type with pleiomorphic or flat vesicles in the presynaptic bouton and only slight postsynaptic density (F, blue asterisk) on the left. Scale = 200 nm. (Rat, lateral geniculate nucleus.) Download the high resolution image.