the role of nitric oxide on the oxytocin induce analgesia in mice

objective(s): analgesic effects of oxytocin and it&apos;s the other physiological effects were well-known. the aim of present study was determination of nitric oxide role on analgesic effects of oxytocin in mice. materials and methods: 216 male albino mice were divided randomly into two experimental groups, tail flick and formalin test. each experimental group consists of three main groups including: saline, l-arginine (50 mg/kg) and l-name (10 mg/kg) intraperitoneal (ip) injection. 15 min after injection in each of the following groups, the animals in each groups divided to the three subgroups including:  saline (n=12), oxytocin (1 mg/kg) (n=12) and oxytocin (1 mg/kg) + atosiban (1 mg/kg) (n=12) was injected ip and then after 30 min of use the formalin test and tail flick were to evaluate the response to pain. results: area under the curve (auc) in the late phase of the formalin test, in sub-groups oxytocin + saline and l-name were significantly decreased compared with saline + saline group (p<0.05 to p<0.001), and auc in l-arginine + saline and atosiban + saline + oxytocin were significantly increased compared with oxytocin + saline group (p<0.05). tail flick tests as well as a significant reduction in the auc in oxytocin + l-arginine and atosiban + saline + oxytocin groups were compared with oxytocin + saline group (p<0.001). conclusion: oxytocin has analgesic effects in the acute and late phase of pain in the formalin test. moreover, exogenous increasing of nitric oxide reduced the analgesic effect of oxytocin.