The discussion and conclusions of this study are based primarily on the main effect of treatment (Tx) and the Tukey post hocanalyses shown in the extreme right column; however, the main effect of time (Time) and the time × treatment interaction (Time × tx) are shown for completeness. The identity of the groups in thepost hoc column is indicated by the numbers that are given in each of the respective figures. In some experiments, the JOR was measured in parallel with the collection of microdialysis fractions. Figure 6 (DA) and Figure 7 (DA) show the statistical analyses of dopamine release induced by capsaicin or morphine, respectively (shown in Figs. 6 and 7). Figure 6 (JOR) and Figure 7 (JOR) show the statistical analyses for the JOR measurements taken in parallel with the microdialysis samples; some microdialysis experiments were done without simultaneous JOR measurements. See Figures 2 and 3 for the effect of morphine or capsaicin, respectively, on the JOR in morphine naı̈ve and tolerant rats.

*Post hoc analyses were not done because there were only two groups or because there was no significant main effect of treatment (i.e., Fig. 4).