Projections of Brn3b+ neurons in the intermediate or deep SC/PAG to other subcortical areas.

(A) Schematic diagram of AAV-mCherry injection into deep SC/PAG. (B–D) Representative images showing mCherry expression in deep SC/PAG (B) and mCherry+ neuronal projections to LP (arrow in C). Magnified view of the boxed area (D). LP was identified by immunostaining with calretinin (CR) antibody (Byun and colleagues [22]) (n = 3 mice; DAPI (blue)). (E) Schematic diagram of AAV-Cre injection into intermediate SC of Brn3bflox/+ mouse. (F, G) Representative images of AP signals in intermediate SC (E) and projections to ventral LGN (arrow in G), indicating that Brn3b+ neurons in the intermediate SC project to ventral LGN (n = 2 mice). Very faint signals in LP (G) might originate from neurons in other layers of the dorsal midbrain. However, if other layers beyond the targeted areas were obviously labeled by the AAV, such animals were excluded from analysis (A–G). Scale bars: 500 μm. (TIF)