Abstract

• This study provides a description of the normal morphology of the synapses of the locus coeruleus in the squirrel monkey, Saimiri sciureus, at the electron microscopic level. The animals were perfused with 2% glutaraldehyde-1% paraformaldehyde fixative in phosphate buffer at pH 7.4. Tissues from the locus coeruleus were postfixed by 2% osmium tetroxide in phosphate buffer at pH 7.4, and dehydrated in graded ethanol and aceton, and embedded in Epon 812. The polymerization was carried out in oven at 60℃. The ultrathin sections were cut on a LKB ultratome, contrasted with uranyl acetate and lead citrate, and examined in a Siemens Elmiskop 1A electron microscope. Special attention during the observation was given to the different types of synapses. Five types of synapses with many characteristics, could be differentiated : small-round vesicle terminals(52%), pleomorphic vesicle terminals(25%), elongated vesicle terminals(16%), small-round and dense core vesicle terminals(5%) and large-round vesicle terminals(2%). Some of the axosomatic synapses with small round or pleomorphic vesicles make an indirect contact to the soma by somatic appendages.