Figure 2. Time course of effects on %MPE in tail flick test (left panel) and colorectal distension test (right panel) after intrathecal challenge test with morphine (Mor) 5 [micro sign]g in rats that received intrathecal infusion of lidocaine (Lid) 200 [micro sign]g [middle dot] kg^-1[middle dot] h^-1(n = 6), Lid 600 [micro sign]g [middle dot] kg^-1[middle dot] h^-1(n = 6), Lid 1000 [micro sign]g [middle dot] kg^-1[middle dot] h^-1(n = 6), or saline (Sal)(n = 7) for 6 days. Lid infusion groups caused no change in the time course effects, the peak (100 %MPE), and duration of peak effect, comparing with Sal infusion group. Time course change in %MPEs in both the TF and CD tests after morphine challenge showed a similar tendency in Lid infusion groups. Data are presented as mean +/− SD. *Significantly different from Sal.