Linalool blocks excitability in peripheral nerves and voltage-dependent Na+ current in dissociated dorsal root ganglia neurons

Linalool is a terpene that occurs as a major constituent of essential oils of many plants of widespread distribution. It possesses several biological and pharmacological activities, including depressant effects on the central nervous system and olfactory receptors. The present study investigated whether linalool affects the excitability of peripheral components of the somatic sensory system. We used sciatic nerve and preparations of intact and dissociated neurons of dorsal root ganglion for extracellular, intracellular and patch-clamp recordings. Linalool concentration-dependently (0.3-2.0 mM) and reversibly blocked the excitability of the sciatic nerve. It inhibited peak-to-peak amplitude of the compound action potential (IC50 was 0.78 +/- 0.04 mM). At 0.8 mM, it reversibly increased rheobase and chronaxy (from 3.2 +/- 0.1 V and 52.4 +/- 4.1 mu s to 4.2 +/- 0.3 V and 71.2 +/- 5.5 mu s (n = 5), respectively) and inhibited with greater pharmacological potency the amplitude of the compound action potential components corresponding to axons with slower velocity of conduction. In a similar concentration range (0.1-6 mM), linalool concentration-dependently and reversibly blocked the generation of action potentials of intact dorsal root ganglion neurons without alteration of resting membrane potential and input resistance, and inhibited the voltage-gated Na+ current of dissociated dorsal root ganglion neurons. In conclusion, we demonstrated that linalool acts on the somatic sensory system with local anesthetic properties, since it blocked the action potential by acting on voltagedependent Na+ channels. This finding is important in showing the potential usefulness of linalool as a pharmacotherapeutic agent. (C) 2010 Elsevier B.V. All rights reserved.