Histologically verified microinjection sites for drug or vehicle microinjections in the VL PAG (A) and recording sites for ON and OFF cells in the RVM (B), in transverse sections simplified by Paxinos and Watson . Vehicle or drug microinjections are depicted with filled circles (A). The open circles indicate microinjections that were accidentally or intentionally performed outside of VL PAG, the effects of which (n = 7) were considered in the study for location specificity. Triangles indicate electrode tips in the RVM (B); in particular white triangles represent ON cells and the black ones represent the OFF cells. Distances (in mm) from the interaural line are indicated.