The seed oil of Plukenetia polyadenia (Pp-oil) is used by the Amazon people against arthritis and rheumatism, spreading it in the arms and legs. The fatty acid composition, antinociceptive effect and toxicity of Pp-oil were investigated. Materials and methods: The Pp-oil was obtained by pressing and its antinociceptive activity was analyzed in models of nociception (acetic acid-induced abdominal writhing, hot plate and formalin tests) in mice and also mechanism of action was determined using acetic acid- indiced abdominal writing, open field, pole test and rotarod.
Results: Pp-oil demonstrated a significant dose dependent antinociceptive effect (p< 0.05) in the chemical stimulation and at the second phase of formalin. However, the result from the hot plate test, open field, pole test and rotarod were not significant (p> 0.05), suggesting that Pp-oil has an analgesic activity, which is putative of peripheral origin. In the writhing test, the oil dosed at 25, 50 and 100 mg/kg reduced the abdominal writhes in a significant manner. In the hot plate test, the oil dosed at 200 mg/kg did not induced alterations in the latency time when compared to the control. At the dose of 100 mg/kg it did not show any difference in motor system proving that Pp-oil does not have any influence at central nervous system. In the formalin test, the oil dosed at 50 and 100 mg/kg reduced in a significant manner the second phase of the algic stimulus. Pp-oil at 100mg/kg did not show any alterations in motor system when analyzed with open field, pole test and rotarod (p>0,05), which corroborates with previous results that affirm Pp-oil has no participation in central nervous system. In addition, its antinociception was reversed by naloxone in evaluation of the mechanism of action.
Conclusion: Pp-oil proved to have analgesic properties. Moreover, the results concerning mechanism suggest that opiod receptors are involved in the antinociceptive action of the Pp-oil using a peripheral pathway.
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