Validity Assessment of 5 Day Repeated Forced-Swim Stress to Model Human Depression in Young-Adult C57BL/6J and BALB/cJ Mice

5d-RFSS paradigm. Experimental timeline of 5d-RFSS in C57BL/6J or BALB/cJ mice. SPT1 and TST1 were performed on days −3 to 0, before stressed mice underwent 10 min of forced-swim stress during 5 consecutive days (days 1–5; induction phase), followed by SPT2 (days 5–8), SPT3 (days 22–25), an OFT (day 36), the last forced swim session (test phase; day 37), TST2 (day 38), and SPT4 (days 38–41). Nonstressed controls were not forced to swim during the induction phase but otherwise underwent the same protocol.

Effects of 5d-RFSS on depressive-like behavior in C57BL/6J mice. A, Immobility time of 5d-RFSS C57BL/6J mice during the induction phase (days 1–5) forced-swim tests (FST; main effect of time, F_(4,36) = 8.68, p = 0.00005; post hoc test, §p = 0.006, §§p = 0.001, §§§p = 0.0002 vs day 1), and of 5d-RFSS and nonstressed control mice during the test phase (day 37; t_(1,18) = 3.44, *p = 0.003 vs nonstressed mice). B, Two-bottle SPTs before 5d-RFSS (SPT1) and after 5d-RFSS (SPT2 to SPT4). C, TST immobility time before 5d-RFSS (TST1) and after 5d-RFSS (TST2; main effect of time, F_(1,18) = 9.14, p = 0.007; post hoc test, §p = 0.007 vs TST1). D–F, Distance traveled (t_(1,18) = 0.43, p = 0.67; D), number of center zone entries (t_(1,18) = 1.01, p = 0.33; E), and number of feces produced during the OFT (t_(1,18) = 0.63, p = 0.53; F). G, Change in body weight (%) from day −3 to 36 (main effect of time, F_(6,108) = 90.48, p < 0.00001; post hoc test, §p = 0.02, §§p = 0.0001 vs day −3). H, I, Food intake during induction phase (days 1–5; t_(1,17) = 0.77, p = 0.45; H) and during days 8–36 (t_(1,18) = 0.71, p = 0.49; I). NS, Not significant. n = 10/group for all experiments.

Effects of 5d-RFSS on depressive-like behavior in BALB/cJ mice. A, Immobility time of 5d-RFSS BALB/cJ mice during the induction phase (days 1–5) of forced swim tests (FST; main effect of time, F_(4,36) = 6.29, p = 0.0006; post hoc test, §p = 0.02, §§p = 0.002 vs day 1) and of 5d-RFSS and nonstressed control mice during the test phase (day 37; t_(1,18) = 3.08, *p = 0.007). B, Two-bottle SPTs before 5d-RFSS (SPT1) and after 5d-RFSS (SPT2 to SPT4; main effect of time, F_(3,54) = 12.67, p < 0.00001; post hoc test, §p = 0.002, §§p = 0.0002 vs SPT1). C, TST immobility time before 5d-RFSS (TST1) and after 5d-RFSS (TST2; main effect of time, F_(1,18) = 5.06, p = 0.04; post hoc test, §p = 0.04 vs TST1). D–F, Distance traveled (t_(1,18) = 0.74, p = 0.47; D), number of center zone entries (E), and number of feces produced during the OFT (t_(1,18) = 0.79, p = 0.44; F). G, Change in body weight (%) from days −3 to 36 (main effect of time, F_(6,108) = 36.96, p < 0.00001; post hoc test, §p = 0.002, §§p = 0.0001 vs day −3). H, I, Food intake during the induction phase (days 1 – 5; t_(1,18) = 0.07, p = 0.94; H) and during days 8–36 (t_(1,18) = 1.36, p = 0.19; I). NS, Not significant; ND, not detected. n = 10/group for all experiments.

CSDS induces a depressive-like state in C57BL/6J mice. A, CSDS mice had greater weight gain compared with nondefeated control (CON) mice (days 1 – 11; t_(1,14) = 2.28, *p = 0.039). B, CON mice did not show a significant decrease in sucrose preference during two-bottle SPT2 compared with SPT1 (t_(1,7) = 1.96, p = 0.1). CSDS mice demonstrated lower sucrose preference during SPT2 compared with SPT1 (before CSDS; t_(1,7) = 3.16, *p = 0.016). C, CSDS mice spent less time in the interaction zone with target present during the social interaction test on day 11 (t_(1,14) = 5.04, *p = 0.00018). D, Locomotor activity did not differ significantly between experimental groups during OFT on day 12 (t_(1,14) = 1.01, p = 0.33). E, CSDS mice enter OFT center zone less than CON mice (t_(1,14) = 2.99, *p = 0.01). NS, Not significant. n = 8/group for all experiments.