opiate system mediate the antinociceptive effects of coriandrum sativum in mice

our previous study showed that coriandrum sativum (cs) has antinociceptive effects, but the mechanisms that mediate this effect are not clear. the present study was designed to test the role of opiate system in the antinociceptive effects of cs on acute and chronic pain in mice using hot plate (hp), tail flick (tf) and formalin (ft) tests and also to compare its effect with dexamethasone (dex) and stress (st).      young adult male albino mice (25-30 g) in 33 groups (n = 8 in each group) were used in this study. cs (125 250, 500 and 1000 mg/kg ip), dex (0.5, 1 and 2 mg/kg ip), vehicle (veh) or swim stress were used 30 min before the pain evaluation tests. acute and chronic pain was assessed by hp, tf and ft models. in addition, naloxone (nal, 2 mg/kg, ip) was injected 15 min before the cs extract administration in order to assess the role of opiate system in the antinociception of cs.      results indicated that cs, dex and st have analgesic effects (p < 0.01) in comparison with the control group and higher dose of cs was more effective (p < 0.001). besides, pretreatment of nal modulates the antinociceptive effects of cs in all models (p < 0.001).      the above findings showed that cs, dex and st have modulator effects on pain. these findings further indicate that the cs extract has more analgesic effects than dex and st and also provides the evidence for the existence of an interaction between antinociceptive effects of cs and opiate system.