Figure 2 - Index of analgesia (IA) in the hot-plate test for the control group (control, N = 8), immediately after induction of the five episodes of tonic immobility (TI, N = 8), and for the group pretreated with naloxone and submitted to TI induction (Nal + TI, N = 8). Time zero represents the baseline and the vertical bars indicate the standard error of the mean. *P<0.05 compared to control and to the Nal + TI group (Duncan test).