Photographs of coronal sections of the caudal part of the neostriatum (St) illustrating the presence of MOR in the MrD. No obvious "patches" of MOR-immunoreactivity was seen. A: A figure at low magnification showed dense accumulation of nerve fibers of MOR-immunoreactivity in the MrD and in the globus pallidus (GP) as well, and weak staining in the rest of the St. B: At higher magnification, the fusiform cell bodies exhibited MOR-immunoreactivity in puncta within parallel-arranged nerve fibers in the MrD (the arrow in B). C: The cell bodies and their dendrites stretched dorsoventrally were showed in the MrD (arrows in C). Scale bars: A, 200 um; B, C, 50 um.