In the chronic FN-439 or aCSF condition, the aCSF-treated animals displayed escalated responding on the second post-dependence test session (t (4) = 2.23, p<0.05). The mixed model ANOVA conducted on the initial and escalated acute withdrawal self-administration sessions following chronic MMP inhibition or aCSF infusion via osmotic minipump (see Figure 3) during the dependence induction period and acute withdrawal test sessions indicated that there was a significant Drug Treatment × Session (F (1,14) = 6.833, p≤0.05). The Drug Treatment × Session interaction indicates that the animals acted differently depending on whether they were treated with chronic FN-439 or aCSF, although post-hoc independent samples t-tests comparing the performance of the chronic FN-439 vs. aCSF-treated rats were non-significant (t (10) = 1.446, p>0.05). The fact that the mixed model ANOVA shows a significant effect displays the importance of using the correct statistical tests (i.e., the use of the mixed-model ANOVA) to avoid making a Type II error (i.e., the null hypothesis is not rejected when it is in fact false).
