Figure 1. Reduced proliferation of striatonigral neurons in Rarb−/− LGE. A–D4, Coronal brain sections of the LGE or striatum (drawings, top left) were analyzed at E13.5 (A and A′), E18.5 (B and B′), and P0 (C1–C4 and D1–D4), following a maternal BrdU injection at E13 (BrdU, green; DAPI, blue) in WT (A, B, C1–C4, and D1–D4) and Rarb−/− mice (A′ and B′). Drd1-expressing cells (C1–C4, red) and Drd2-expressing cells (D1–D4, red) were identified by fluorescent ISH and their overlap with BrdU immunolabeling is illustrated for WT dorsal striatum at P0 (C2–C4 and D2–D4). C4, D4, I, Details of colabeled cells are indicated by arrows at higher magnification for Drd1 (C4) and Drd2 (D4), whereas respective cell counts are shown in I. E–H′, Expression of Drd1 (E and E′), Pdyn (F and F′), Chmr4 (G and G′) and Drd2 (H and H′) were tested at E18.5 and are shown for WT (E,F,G,H) and Rarb−/− (E′, F′, G′, and H′) striatum. J, mRNA expression of striatonigral (Drd1, SP) and striatopallidal markers (Drd2, Penk, Adora2a) was quantified by qRT-PCR in E18.5 LGE preparations. Scale bars: A, 500 μm; B, 200 μm; C1, 50 μm; E, 200 μm. *p < 0.05, **p < 0.01, ***p < 0.001 compared with WT group (Student's t test). Error bars represent SEM.