M. Tsunozaki and R. C. Lennertz contributed equally to this work.
A ‘toothache tree’ alkylamide inhibits Aδ mechanonociceptors to alleviate mechanical pain
Article first published online: 12 JUN 2013
© 2013 The Authors. The Journal of Physiology © 2013 The Physiological Society
The Journal of Physiology
Volume 591, Issue 13, pages 3325–3340, July 2013
How to Cite
Tsunozaki, M., Lennertz, R. C., Vilceanu, D., Katta, S., Stucky, C. L. and Bautista, D. M. (2013), A ‘toothache tree’ alkylamide inhibits Aδ mechanonociceptors to alleviate mechanical pain. The Journal of Physiology, 591: 3325–3340. doi: 10.1113/jphysiol.2013.252106
- Issue published online: 1 JUL 2013
- Article first published online: 12 JUN 2013
- Accepted manuscript online: 12 MAY 2013 03:21AM EST
- (Resubmitted 23 January 2013; accepted after revision 3 May 2013; first published online 7 May 2013)
- • Extracts from the toothache tree (Zanthoxylum) are used to treat inflammatory pain, such as toothache and arthritis.
- • Hydroxy-α-sanshool (sanshool) is a major alkylamide in extracts from Zanthoxylum plants.
- • Sanshool treatment in mice caused a selective attenuation of mechanical sensitivity under naïve and inflammatory conditions
- • Sanshool inhibits Aδ mechanonociceptors that mediate both sharp acute pain and inflammatory pain, and inhibits the activity of multiple voltage-gated sodium channel subtypes, among which Nav1.7 is the most strongly affected.
- • Our data implicate Nav1.7 as a key mediator of inflammatory mechanical pain in ‘fast pain’ mechanosensory neurons.
Abstract In traditional medicine, the ‘toothache tree’ and other plants of the Zanthoxylum genus have been used to treat inflammatory pain conditions, such as toothache and rheumatoid arthritis. Here we examined the cellular and molecular mechanisms underlying the analgesic properties of hydroxy-α-sanshool, the active alkylamide produced by Zanthoxylum plants. Consistent with its analgesic effects in humans, sanshool treatment in mice caused a selective attenuation of mechanical sensitivity under naïve and inflammatory conditions, with no effect on thermal sensitivity. To elucidate the molecular mechanisms by which sanshool attenuates mechanical pain, we performed single fibre recordings, calcium imaging and whole-cell electrophysiology of cultured sensory neurons. We found that: (1) sanshool potently inhibits Aδ mechanonociceptors that mediate both sharp acute pain and inflammatory pain; (2) sanshool inhibits action potential firing by blocking voltage-gated sodium currents in a subset of somatosensory neurons, which express a unique combination of voltage-gated sodium channels; and (3) heterologously expressed Nav1.7 is most strongly inhibited by sanshool as compared to other sodium channels expressed in sensory neurons. These results suggest that sanshool targets voltage-gated sodium channels on Aδ mechanosensory nociceptors to dampen excitability and thus induce ‘fast pain’ analgesia.