Study of anti-nociceptive effects of Cinnamomum and its interactions with opioidergic, dopaminergic, serotoninergic and histaminergic pathways in mice

Considering the effects of Cinnamomum in pain control and lack of report on its ani-nociceptive activity, the aim of this study is to investigate the analgesic effects of Cinnamomum extract in the hot plate test and its interactions with opioidergic, dopaminergic, serotoninergic and histaminergic pathways in mice. In experiment 1, animals injected (i.p) with saline, Cinnamomum extract (100, 200 and 400 mg/kg) and morphine (5mg/kg). After determining effective dose of the, Cinnamomum extract experiments 2-5 were done. In experiment 2, animals injected with saline, Cinnamomum extract (400mg/kg), naloxone (2mg/kg) and co-injection of the Cinnamomum extract + naloxone. Experiments 3-5 were similar to experiment 2, except mice injected with cimetidine (12.5mg/kg), 6-HODA (100 mg/kg) and cyproheptadine (4mg/kg) instead of naloxone. Then, mice were individually placed on a hot plate device and pain tolerance was measured at first, 30, 45 and 60 minutes later and compared with the baseline. According to the results, morphine significantly increased the delay time in pain perception (P<0.05). The Cinnamomum extract (400 mg/kg) significantly increased the delay time in pain perception after 30 minutes (P<0.05). Co-injection of cyproheptadine with Cinnamomum extract after 30 minutes significantly reduced pain perception delay time (P<0.05). Co-administration of cimetidine with Cinnamomum extract after 30 minutes significantly reduced delay time in pain perception (P<0.05). The combined administration of 6-hydroxydopamine with Cinnamomum extract after 30 minutes significantly decreased the delay time in pain perception (P<0.05). The results show that Cinnamomum extract has analgesic activity and these effects are mediated with opioidergic, dopaminergic and serotoninergic systems.