FIG. 1.

Individual globus pallidus (GP neurons form sparse terminal fields in the subthalamic nucleus (STN). A and B: light micrographs of single GP neurons that were juxtacellularly labeled in vivo. In A, the tissue has also been immunolabeled for parvalbumin, which is expressed by a subpopulation of neurons in the GP. The juxtacellularly labeled GP neuron, which was revealed using diaminobenzidine (DAB) in the presence of Ni²⁺, is easily distinguished from parvalbumin immunoreactive neurons, which were revealed using DAB, on the basis of labeling intensity and color (not apparent here). C, 1 and 2: labeled axonal boutons (small arrows) arising from a GP axon occurred in small clusters that were distributed at low density across the STN. The dashed lines mark the boundary between the striatum (CPu) and GP in A and B and the boundary between the zona incerta (ZI) and the STN in C1 and C2. The internal capsule (IC) underlying the STN is visible in C1. Scale in A also applies to B. Scale in C1 also applies to C2.