Figure 2

Lepr cKO mice exhibit depression-like behaviors. (a, b) Locomotor activity. Locomotor activity was monitored for 30 min and analyzed in 2-min bins. The inserts indicating the total distance traveled during the 30-min test. Male fWT, n=10; male Lepr cKO, n=11; female fWT, n=8; female Lepr cKO, n=10. (c) Tail suspension test. Immobility time was measured during the 6-min test period. Male fWT, n=8; male Lepr cKO, n=11; female fWT, n=7; female Lepr cKO, n=10. ^**P<0.01 compared with the littermate fWT control group. (d) Forced swim test in both males and females. Immobility time was measured during the last 4 min of the 6-min test period. Male fWT, n=10; male Lepr cKO, n=11; female fWT, n=8; female Lepr cKO, n=9. ^*P<0.05, ^***P<0.001 compared with the littermate fWT control group. (e) Sweet solution preference tests in males expressed as percent sucrose solution (1%) or saccharin (0.01%) intake within a 4-day test (sucrose or saccharin solution intake/total intake × 100). Left y axis, sucrose preference; n=18 per group. Right y axis, saccharine preference; n=9 for fWT, n=10 for Lepr cKO. ^*P<0.05 compared with the littermate fWT control group. (f) Learned helplessness test in male mice. (Left panel) Escape latency. (Right panel) Number of failures to escape; n=10–13 per group. ^*P<0.05, ^***P<0.001 compared with the fWT, Shock group. (g) Social interaction and avoidance in male mice. (Top) Representative tracks of control (left) or socially defeated (right) fWT or Lepr cKO mice in an arena in the presence of an aggressive CD1 mouse in the target area. (Bottom-left panel) Time spent in the interaction zone. (Bottom-middle panel) Time spent in the avoidance zone. (Bottom-right panel) Social preference ratio defined as time in the interaction zone/(time in the interaction zone + time in the avoidance zone) × 100. n=8–11 per group. ^**P<0.01, ^***P<0.001 compared with respective control condition in fWT and Lepr cKO mice; ^#P<0.05, ^##P<0.01 compared with defeated fWT mice. All data are expressed as mean±s.e.m.