Projection of 5-HT neurons from the dorsal raphe nucleus (DRN) to the prefrontal cortex (PFC) of mice. Schematic illustrations of the injection site (symbols) in the PFC (A). The image shows the extent of FG diffusion at the injection site (B). Location of the DRN in a coronal section of mouse brain (C). Tph2-immunoreactivity was noted in the DRN (D, E). Cells in the DR after the microinjection of FG into the PFC (F). Double-labeling experiments showed that FG-positive cells overlapped Tph2-positive cells in the DRN (G). Scale bars = 50 μm (B and D). Aq: aqueduct of the cerebrum.