Paroxetine (PRX) dose-dependent changes in the syndrome intensity of rats pretreated with clorgyline (CLG, 2 mg/kg, s.c.) once daily for 3 days. Experiments were carried out on day 4. Data represent mean (±SEM) total intensity score, obtained from five to eight animals/group. (a) Animals were challenged with CLG+veh (control), CLG+1 mg/kg PRX, or CLG+5 mg/kg PRX. Note that the 15 mg/kg data are a replot of Figure 2b. The y axis represents the mean summation of five behavioral components (tremor, forepaw treading, hindlimb abduction, Straub tail, and immobility). PRX in combination with CLG produced a dose-dependent effect on the syndrome intensity. **P<0.01; ***P<0.001 vs the control (CLG+veh) group. (b) Animals were injected with vehicle (veh group), 2 mg/kg M100907 (M10 group), or 0.25 mg/kg MK-801 (MK group), 30 min before the challenge injection of CLG+PRX with the PRX dose at 15 mg/kg. Compared with the vehicle control, syndrome intensity was significantly reduced in animals pretreated with M100907 or MK-801. *P<0.05 and ***P<0.001 vs control (veh+CLG+PRX) group.