Histochemical characteristics of the target cell cluster of TM15.5 axons. A–E, Five serial coronal sections (20 μm thick), from anterior (A) to posterior (E), prepared from a P21 Neurog2CreER(G2A); Cdhr1tTA; TREtdTomato-sypGFP mouse that was given TM at E15.5. Arrowheads show the cell cluster targeted by TM15.5 axons. The TM15 axons expressing tdTomato (A, C, E) and synaptophysin-GFP (C) reporters densely project to the target cell cluster stained with DAPI (A”–E”). The target cell cluster expresses DARPP (A’, E’), dopamine receptors D1R (B’, D), but not D2R (D’). Dopaminergic axons expressing tyrosine hydroxylase (C’) project over this cell cluster. Representative images from three mice. F, Enlarged image of neurons in the cell cluster, which express DARPP (green) and are projected by the tdTomato-expressing TM15.5 axons (red). Scale bars = 500 μm (A–E) and 10 μm (F).