Shape and size of synaptic vesicles in different types of presynaptic profiles in the medial septal nucleus of the rat.

Long and short axis diameters of synaptic vesicles were obtained from 6 classes of presynaptic boutons found in the medial septal nucleus (MS) of the rat. The variability of vesicle size and shape was documented in diagrams and discussed with regard to their suitability as criteria of classification and their functional significance. The variability in shape, but not in size, of vesicles in synapses of Gray's type I is lower than of those in Gray's type II synapses.