Effects of (-)-Linalool in the acute hyperalgesia induced by carrageenan, L-glutamate and prostaglandin E2

A series of studies performed in our laboratory have shown that ( -)-linalool, the natural occurring enantiomer in essential oils, possesses anti-inflammatory and antinociceptive effects in different animal models. The antinociceptive effect of ( -)-linalool has been ascribed to the stimulation of the cholinergic, opioidergic and dopaminergic systems, to its local anesthetic activity and to the blockade of N-Methyl-Daspartate (NMDA) receptors. In this study, we investigated the effect of systemic administration of ( -)-linalool in the paw withdrawal test in rats, a model of thermal hyperalgesia induced by monolateral subplantar injection of carrageenan, L-glutamate or prostaglandin E-2. Carrageenan and L-glutamate induced a hyperalgesic effect on the injection side. Tn contrast, prostaglandin E-2 induced hyperalgesia in both the injection side and the contralateral side. Pretreatment with ( -)-linalool (50-150 mg/kg) inhibited the development of acute hyperalgesia induced by carrageenan in the injected paw, with no effect on the contralateral paw. Furthermore, ( -)-linalool at the highest dose used (200 mg/kg), reduced and reverted the decrease in paw withdrawal latencies induced by L-glutamate on the ipsilateral side, showing antibyperalgesic and antinociceptive effects. An antinociceptive effect was apparent also in the contralateral paw. Finally, (-)-linalool (200 mg/kg) increased paw withdrawal latency on the side contralateral to prostaglandin E-2 injection, but not on the side of the injection. The efficacy of (-)-linalool in decreasing the hyperalgesia induced by carrageenan, L-glutamate and prostaglandin E-2 Suggests that this compound might be useful in pain conditions sustained by the development of neuronal sensitization. (C) 2004 Elsevier B.V All rights reserved.