The Journal of comparative neurology
-
Neurons containing gamma-aminobutyric acid (GABA) in the medial portion of the adult rat nucleus accumbens were characterized with respect to their ultrastructure, sites of termination, and catecholaminergic input. Antisera against GABA-conjugates and the catecholamine-synthesizing enzyme, tyrosine hydroxylase (TH), were localized within single sections by means of peroxidase-antiperoxidase (PAP) and immunoautoradiographic labeling methods. Peroxidase reaction product indicating GABA-like immunoreactivity (GABA-LI) was seen in medium-size (15-20 microns) perikarya containing either round and unindented or invaginated nuclear membranes. ⋯ A few of the unlabeled dendrites, as well as those containing GABA-LI, received symmetric synapses from both catecholaminergic and GABAergic terminals. We conclude that in the medial portion of the rat nucleus accumbens, GABA is localized to two morphologically distinct types of neurons, one or both of which receive monosynaptic input from catecholaminergic afferents, and that GABAergic terminals form symmetric synapses on other principally non-GABAergic neurons. The results also support earlier physiological evidence showing that GABA may modulate the output of other GABAergic and non-GABAergic neurons through presynaptic associations.