Figure 3: Effects of chronic stress on expression and reinstatement of cocaine-induced CPP in WT and D2R–/– mice.
From: Role of dopamine D2 receptors in plasticity of stress-induced addictive behaviours
(a) Experimental protocol for determination of the effect of chronic stress implemented before cocaine conditioning on the expression of CPP (P, pretest; C, conditioning; T, CPP test). (b) CPP score for the protocol in a was calculated as the percentage of time spent by mice (n=4 per group) in the cocaine-paired compartment during the test session minus the percentage of time spent in the same compartment during the pretest session (genotype effect F1,12=0.01, P=0.9229; stress effect F1,16=0.03, P=0.8547; interaction F1,12=0.31, P=0.5897). (c) Experimental protocol for determination of the effects of chronic stress during withdrawal after cocaine conditioning on cocaine-induced CPP and cocaine-primed reinstatement (RI) as shown in d and e, respectively. (d) CPP score (n=4 per group, stress effect F1,12=0.0448, P=0.836; genotype × stress interaction F1,12=21.67, P=0.0006). (e) Cocaine-primed RI of CPP (n=3–4 mice per group, genotype × stress interaction F1,10=7.57, P=0.025). The RI score was calculated as the percentage of time spent in the cocaine-paired compartment during the RI session minus the percentage of time spent in the same compartment during the extinction test session. Two-way analysis of variance post hoc test: *P<0.05, **P<0.01 versus non-stressed (NSt) mice; †P<0.05 versus WT mice. All data are means±s.e.m.
