Fig. 2. Pronociceptive effects of remifentanil when infused over a 30- or 60-min period in the Hargreaves and von Frey tests. Results are expressed as mean value; vertical bars indicate SD. Each point indicates the variation of the response respect to the baseline, normalized to the control group (n = 6), represented by the horizontal broken line . In the graphs, negative values indicate pronociceptive effects. The histograms show the mean overall effects of the treatments obtained from the area above the time–effect curves (AACs). * P < 0.05 compared with control group. ( A ) Pronociceptive effects of 0.66 or 1.33 μg · kg−1· min−1(40 μg/kg) remifentanil, administered over 30 min ( empty squares , n = 8) or 60 min ( filled squares , n = 6). ( B ) Pronociceptive effects of remifentanil administered at 1.33 μg · kg−1· min−1during 30 min (total dose 40 μg/kg, empty squares , n = 6) or 60 min (total dose 80 μg/kg, filled squares , n = 6).