Effects of Papaver rhoeas (L.) extract on formalin-induced pain and inflammation in mice.

Stress amelioration can improve its metabolic as well as other side effects. In the present study, the effects of hydro-alcoholic extract of Papver rhoeas (L.) on formalin-induced pain and inflammation were investigated in male Swiss-Webster mice (20-25 g). Formalin injects in the plantar portion of mice hind paw and pain was studied for 60 min. The plant extract and other drugs were administered intraperitoneally 30 min before formalin. Experiments showed that administration of extract (25, 50 and 100 mg kg(-1)) could induced analgesia in a dose-response manner in both phases of formalin test. More over, the extract inhibits inflammation induced by formalin injection. Naloxone (4 mg kg(-1)), dextromethorphan (20 mg kg(-1)) and NG-nitro-L-arginine-methylester (L-NAME; 10 mg kg(-1)) reduced the extract analgesia in first but not late phase. Extract administration also increased plasma corticosterone level in dose-dependent manner. It could be concluded that Papaver rhoeas (L.) extract could inhibits acute phase of formalin test in mice by opioidergic, glutamatergic and nitricergic mechanisms. In addition, the extract can induce corticosterone plasma level which may be responsible for inhibition of inflammation and chronic phase of pain induced by formalin.