Many evidence indicated that glucocorticoids have modulatory effects on pain and probably one of the mechanism that mediate these effects is nitric oxide. The aim of this study was determine of interaction between Corticosterone and Nitric oxide (NO) system on acute (Neurogenic) and chronic (Inflammatory) pain in Formalin Test (FT) model in mice.

In this experimental study we used 70 male albino mice (25-30 gr) in 7 groups. Also we used of Formalin test for evaluation of acute and chronic pain. The criteria for evaluation of pain was measure of all time that animal reaction to pain responses after of injection of formalin (5%) in sub-plantar area of the right hind paw in each of 5 min, during 40 min. All animals received two IP injection, L-Name (10 mg/kg) as a NO synthesis inhibitor or L-Arginin (20 mg/kg), as a NO precursor 60 min and different doses of Corticosterone (1and 3 mg/kg) or Vehicle (Propylene glycol 40% + Saline in 6 ml) were injected 30 min before of FT.

Analysis of data indicated that Corticosterone at doses of 1 and 3 mg significantly reduced pain reaction in mice. Also pretreatment of L-Name enhanced the analgesic effects of Corticosterone in FT, while injection of L-Arginin, as a NO precursor had not significantly effects.

The findings indicated that glucocorticoids induce analgesic effects through modulation of NO system.

Keyword: 

Pain, Glucocorticoids, Formalin Test, Nitric oxide, L-NAME, L-Arginin, Mice