Injection of adeno-associated virus-encoded ChR2-YFP in the DR, PPN, and STN targets YFP expression to each nucleus and its projection targets. A, Horizontal sections from mice injected with virus into PPN, STN, and DR, demonstrate YFP expression (green) throughout the nucleus 4 weeks after injection. DLL, Dorsal nucleus of the lateral meniscus; LPB, lateral parabrachial nucleus; LPBE, LPB external part; MiTg, microcellular tegmental nucleus; MPB, medial parabrachial nucleus; mRt, mesencephalic reticular formation; PaR, pararubral nucleus; PSTh, parasubthalamic nucleus; SNCD, substantia nigra, compact part, dorsal tier; SNR, substantia nigra, reticular part. B, Ovals represent the distribution of labeled neurons for mice used for control (magenta) and cocaine-injected (yellow) mice. C, YFP-labeled afferents (yellow) from PPN, STN, and DR are seen among anti-tyrosine hydroxylase-labeled dopamine neurons (magenta) in SNC.