(A) Schematic of AAV2-hSyn-ChR2-mCherry injections into bilateral vlPAG.
(B) Sample horizontal slice with bilateral virus injection sites into the vlPAG marked in magenta (Aq, aqueduct; DR, dorsal raphe; scale bar, 500 μm).
(C) Cell bodies in the PAG with mCherry expression (magenta; scale bar, 250 μm).
(D) Sample horizontal brain slice with mCherry-fiber expression and TH immunocytochemical labeling, acquired and stitched with 2D slide scan in MBF Stereoinvestigator (green; scale bar, 250 μm).
(E and F) Confocal images at high magnification of TH(+) neurons (green) in the VTA surrounded by mCherry bouton-like profiles (E) and axon fibers (F) from the vlPAG (magenta; scale bar, 20 μm).