CR+/Sp8+ cells in the adult human striatum are extremely rare. A, CR/Sp8 double-immunostained coronal section of the adult human striatum (caudate nucleus). B–E, Higher-magnification images of boxed areas in A show CR+ cells and CR+/Sp8+ cell (C, arrow). Note that CR+ cells were abundant, whereas CR+/Sp8+ cells were extremely rare in the adult human striatum. Scale bar: A, 500 μm; (in B) B–E, 20 μm.