Ultrastructural study of cholecystokinin-like immunoreactive nerve terminals in the rat nucleus accumbens

The cholecystokinin (CCK)-like immunoreactive nerve terminals were studied in the caudal and medial parts of the rat nucleus accumbens (NA), using the indirect immunoperoxidase technique, at the electron microscopic level. In the labelled axon terminals the immunoprecipitate is localized inside large dense-cored vesicles which are occasionally present, and surrounds small and medium-sized, round, clear synaptic vesicles. The immunoreactive nerve terminals participate in synapses of both asymmetrical and symmetrical types containing mostly small synaptic vesicles. The asymmetrical synapses are much more numerous and mainly axo-spinous. The symmetrical synapses are less frequent and are axo-dendritic or axo-somatic.