Figure 1From: Isobolographic analysis of the opioid-opioid interactions in a tonic and a phasic mouse model of induced nociceptive painDose–response curves for the antinociceptive activity in the writhing test of mice induced by fentanyl, methadone, morphine and tramadol. Each point is the mean ± SEM of six animals. % MPE = antinociception represented as a percentage of maximum possible effect.Back to article page