Evaluation of analgesic and anti-inflammatory effect of nanoparticles of magnesium oxide in mice with and without ketamine.

OBJECTIVES According to importance and increasing application of nanoparticles and their toxicity, the identification effects of nanoparticles on physiological systems are essential. Some studies show magnesium has analgesic effect in some pain models but this evaluation was not carried on nano-magnesium oxide (MgO). Thus, present study was designed to evaluation effect of Mgo nanoparticles alone and in combination with ketamine on two pain and inflammation model in mice. MATERIALS AND METHODS At this study, adult male mice was used which had 29±3 gram weight. Formalin and acetic acid tests were carried. Acetic acid (1%) was intraperitoneally injected 0.3ml and the abdominal writhing was counted from 10 to 30 minutes after it. Formalin (2.5%) was injected 0.04 ml/mouse subcutaneously in plantar site of mice.  The time of licking was cumulatively measured 0-5 (acute phase) and 15-25 (chronic phase) minutes later. Control (negative control), ketamine (0.1 mg/kg), MgO nanoparticles (5 and 10 mg/kg), conventional MgO (5 and 10 mg/kg) and ketamine with conventional and nanoparticles MgO groups were studied in both tests. RESULTS Mean of writhing was significantly decreased by all drugs with comparison to control group (p = 0.0001). This decreasing was significant between conventional and nanoparticle MgO. The time of licking at both acute and chronic phases of formalin test was significantly decreased by all drugs with comparison to control group. However, this mean had significant difference with MgO nanoparticles. CONCLUSIONS It seems that the nano-MgO induces analgesic and anti-inflammatory effects through central and peripheral mechanisms at experimental formalin and acetic acid testes and potentiates effect of ketamine.