Experimental Brain Research

, Volume 236, Issue 6, pp 1767–1774 | Cite as

Inhibitory effects of eugenol on putative nociceptive response in spinal cord preparation isolated from neonatal rats

  • Saki Yagura
  • Hiroshi Onimaru
  • Koji Kanzaki
  • Masahiko Izumizaki
Research Article


Eugenol is contained in several plants including clove and is thought to exert an analgesic effect. It has been suggested that the slow ventral root potential induced by ipsilateral dorsal root stimulation in the isolated (typically lumbar) spinal cord of newborn rats reflects the nociceptive response, and this in vitro experimental model is useful to assess the actions of analgesics. To further elucidate neuronal mechanisms of eugenol-induced analgesia, we examined the effects of extracellularly applied eugenol on the nociceptive spinal reflex response. To evaluate the effects of eugenol on putative nociceptive responses, the ipsilateral fifth lumbar (L5) dorsal root was stimulated using a glass suction electrode, and the induced reflex responses were recorded from the L5 and twelfth thoracic (Th12) ventral roots in spinal cord preparations (Th10–L5) from newborn rats (postnatal day 0–3). We found that eugenol (0.25–1.0 mM) caused dose-dependent attenuation of the reflex response and also depressed spontaneous ventral root activity. We also found that the slow ventral root potential was further divided into two components: initial and late components. A lower concentration of eugenol selectively depressed the late component. The inhibitory effects by 1.0 mM eugenol were not reversed by 10 µM capsazepine (TRPV1 antagonist) or 40 µM HC-030031 (TRPA1 antagonist). The depressive effect of eugenol on the reflex response was also confirmed by optical recordings using voltage-sensitive dye. Our report provides additional evidence on the basic neuronal mechanisms of eugenol to support its clinical use as a potential analgesic treatment.


Eugenol Nociceptive response Slow ventral root potential Newborn rat In vitro 



This work was partially supported by Grants-in-Aid for Scientific Research (KAKENHI: 25430012).

Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflict of interest.

Supplementary material

221_2018_5254_MOESM1_ESM.avi (2 mb)
Voltage imaging of the reflex response in the ventral spinal cord induced by L5 dorsal root stimulation, corresponding to Fig. 4A (AVI 2034 KB)


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Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2018

Authors and Affiliations

  • Saki Yagura
    • 1
    • 2
  • Hiroshi Onimaru
    • 1
  • Koji Kanzaki
    • 2
  • Masahiko Izumizaki
    • 1
  1. 1.Department of PhysiologyShowa University School of MedicineTokyoJapan
  2. 2.Department of Orthopaedic SurgeryShowa University Fujigaoka HospitalKanagawaJapan

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