Fig. 2.
The ultrastructural appearance of Homer, seen with pre-embedding immunoperoxidase labeling. The DAB reaction product is confined to synapses, where it is always restricted to the postsynaptic aspect. (A) a bouton (b) makes two synapses (arrowheads), both of which show DAB labeling. (B) The central bouton of a type I glomerulus (CI) can be recognized because of its indented contour, lack of mitochondria and the presence of densely packed synaptic vesicles of highly variable size. Three of the synapses (arrowheads) formed by the central bouton are strongly labeled with DAB. (C) The central bouton of a type II glomerulus (CII) can be identified because of its large size and numerous mitochondria. It forms several synapses with adjacent peripheral profiles, and two of these (arrowheads) are clearly DAB-labeled. Scale bar = 0.5 μm.