Figure 1: Behavioural responses to stress in WT and D2R–/– mice.
From: Role of dopamine D2 receptors in plasticity of stress-induced addictive behaviours
(a–e) Mice (n≥7 per group) were subjected to the elevated plus-maze test after exposure to restraint stress for 0.5, 2 or 6 h, or for 2 h daily for 14 days. Non-stressed (NSt) animals were examined as a control. The percentage of entries into (a, c) and the time spent in (b, d) the open arms (a, b) or closed arms (c, d), as well as the percentage of head-dipping time in the open arms (e) were determined. (a) Stress effect F4,77=2.7, P=0.036; genotype effect F1,77=12.84, P=0.0006. (b) For NSt versus 2 h/14 day, stress effect F1,30=3.8, P=0.06. (c) Stress effect F4,79=3.29, P=0.0152; genotype effect F1,79=12.11, P=0.0008. (d) Stress effect F4,87=5.11, P=0.001; genotype effect F1,87=23.14, P<0.0001. (e) Stress effect F4,80=5.49, P=0.0006; genotype effect F1,80=36.25, P<0.0001. (f) Immobility time of mice (n=4–10 per group) in the forced swim test after chronic stress (stress effect F1,29=24.28, P<0.0001; genotype effect F1,29=9.35, P<0.0048). (g) Distance travelled by mice (n≥7 per group) in the central zone in the open-field test after acute or chronic restraint stress (stress effect F4,86=14.74, P<0.0001; genotype effect F1,86=53.68, P<0.0001). (h) Plasma concentration of corticosterone in mice (n=6–20 per group) at 0, 30 and 60 min after the end of each stress session on days 1, 7 and 14 of the chronic stress protocol, as well as on days 1, 3, 7 and 14 of recovery (R) after the stress protocol. For 60 min after stress on days 1, 7 and 14: stress effect F1,30>4.29, P<0.05; genotype effect F1,30>10.8, P<0.0026; interaction F1,30>4.29, P<0.05. For day 1 of recovery: stress effect F1,60=9.31, P=0.0034; genotype effect F1,60=11.06, P=0.0015; interaction F1,60=4.01, P=0.0498. For day 3 of recovery: genotype × stress interaction F1,21=1.83, P=0.1906. Two-tailed Student’s t-test for (a–d): †P<0.05, ††P<0.01 versus WT mice. One-way analysis of variance (ANOVA) post hoc test for a–d: *P<0.05, **P<0.01, ***P<0.001 versus NSt mice. Two-way ANOVA post hoc test for e–h: *P<0.05, **P<0.01, ***P<0.001 versus NSt mice; †P<0.05, ††P<0.01, †††P<0.001 versus WT mice. All data are means±s.e.m.
