Time of immobility under different testing conditions and effects of chronic treatment with fluoxetine (FLX) and imipramine hydrochloride (IMI). (a) Time of immobility of the 12-h light, 12-h dark (LD), continuous darkness (DD), and photoreceptor-ablation-DD (MNU-DD) groups measured using the tail suspension test (TST). LD group serves as control (one-way ANOVA; **p<0.001). (b) Time of immobility of the MNU-DD-vehicle (MNU-DD-VEH-3), MNU-DD-anti-CTB-saporin immunotoxin (MNU-DD-anti-CTB-SAP), and MNU-DD-tetrodotoxin (MNU-DD-TTX) groups measured through TST, MNU-DD-VEH-3 group serves as control (one-way ANOVA; **p<0.001). (c) Forced Swimming test (FST) climbing, swimming, and immobility scores for saline (VEH), FLX, and IMI chronic treatment. DD-VEH-2 group serves as control. One-way ANOVA; *p<0.05; **p<0.001. (d) The effect of FLX and IMI chronic treatment on immobility during TST. DD-VEH-2 group serves as control. One-way ANOVA; **p<0.001.