60% of pERK expressing neurons in the RVM are also serotonergic. Confocal images of ERK activation in the RVM 8 days post-SNI surgery. Colocalization of ERK expressing neurons (green) and TPH expressing neurones (red). The single staining for each antibody and the merged image are shown from left to right and double staining appears in yellow. Notice the extensive staining of dendrites (arrow heads). Arrows show non double labeled neurons. Scale bar, 200 μm.