interaction between analgesic effect of nano and conventional size of zinc oxide and opioidergic system activity in animal model of acute pain

introduction: today nano-medicine tries to produce new drugs to reduce the dosage and side effects of their conventional forms. according to the interaction between zinc and opioidergic system activity, this study has investigated the effect of new kind of zinc supplement, nano zinc oxide (nzno), in compared to its conventional form (czno), in presence and absence of opioidergic system activity on acute pain.  methods: adult male wistar rats (weighting 200±20gr) divided into groups: control (receiving saline %0.9), nzno (1, 5, 10, 20 mg/kg), czno (1, 5, 10, 20 mg/kg), naloxone 1mg/kg, morphine 6 mg/kg, and co- injected groups of morphine and/or naloxone with nzno (5mg/kg) and/or czno 10 mg/kg. hot plate assay was used to evaluation of nociception and post injected latencies were recorded every 30 min for 90 min after i.p. injections of drugs. in co-injected groups latency time recorded after 60 minutes.  results: data indicated that both of zno supplements reduced latency time in dose and time dependent on the effect of nzno was higher than czno. also these components could improve anti-nociception effect of morphine and naloxone could not change the effect of these supplements.  discussion: it seems that nzno has more efficacy than its conventional form to showing analgesic effect that probably is related to the physicochemical properties of nzno. also may be these supplements have interaction with opioideric system in body.