Fig. 4

Expression of 5-HT fibers in LC and VTA. In LC (a, b) and VTA (c, d), triple positive axon fibers were confirmed (white rectangles). These fibers represent B9 5-HT-derived axons since AAV was locally injected into B9. G-CaMP6/mCherry positive soma and axons were hardly observed outside SERT positive structures. In LC (b) and VTA (d), G-CaMP6/mCherry double-positive fibers were found not only near TH positive cell body but also TH negative areas (yellow rectangles) within the nucleus, indicating B9 5-HT neurons project to not only catecholaminergic neurons (NA in LC and DA in VTA) but also other neurons in the target nuclei. Scale bar length:100 μm