Inhalant Linalool induces antinociception mediated by opioid mechanism

[Speaker] Takaaki Komatsu:1
[Co-author] Soh Katsuyama:2, Kakuyou Ogawa:3, Kenji Tabata:1, Tsukasa Sakurada:1
1:Department of Drug analysis, Daichi university of pharmacy, Japan, 2:Center for experimental pharmacy practice, Tokyo university of pharmacy and life sciences, Japan, 3:Department of Natural medicines, Daiichi university of pharmacy, Japan

 Linalool is a natural occurring enantiomer monoterpene compound prevalent in essential oils of various aromatic plant species. Recent studies suggest that linalool has anti-inflammatory, antihyperalgesic and antinociceptive properties in different animal models. Our laboratory has previously shown that intraplantar injection of Linalool reduced the nociceptive response as assayed by capsaicin test and the mechanical allodynia induced by partial sciatic nerve ligation in mice. In this study, the antinociceptive effect of inhaled linalool was evaluated in mice. Inhaled for 60 min linalool at 0.1% significantly reduced the acetic acid-writhing response. Intraperitoneal (i.p.) pretreatment with naloxone, an opioid receptor antagonist, significantly reversed linalool-induced antinociception. In the hot plate test, analgesic activity observed after inhaled for 60 min linalool at 1.0 % was inhibited by naloxone i.p. pretreatment, suggesting the involvement of opioidergic pathways. Inhalant treatment with analgesic doses of linalool did not affect mice spontaneous locomortor activity. The antinociception induced by the inhalation of linalool was prevented on mice prepared by intranasal irrigation with zinc sulfate. This result suggests that the inhalation of linalool shows antinociception through the olfactory nervous function. In conclusion, linalool reveals an analgesic activity mainly relevant mediated by opioid mechanism after inhalation, at doses devoid of sedative side effect, suggesting the interest for potency application of linalool in aromatherapy.
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