Fig. 2

Effect of venlafaxine (VEN) on the morphine analgesia. a Effect of venlafaxine (20 mg/kg) in the tail-flick test, and b effect of venlafaxine in the hot-plate test. Venlafaxine in combination with morphine produce a significant increase in % MPE in both the tail-flick (p < 0.05; a) and hot-plate assays (p < 0.05; b) as compared to the morphine-treated rats. The peak value of this group was observed at 30 min after administration of morphine in analgesia tests. Each point represents the mean ± SEM of percent of maximal possible effect (% MPE) for 7 rats. *p < 0.05 compared to the morphine-treated group and **p < 0.01 compared to saline-treated group