Intrathecal eugenol administration alleviates neuropathic pain in male Sprague‐Dawley rats

Abstract

The main objective of this study was to determine the central effect of eugenol on neuropathic pain when injected intrathecally at the level of the lumbar spinal cord. In a preliminary study the penetrability of eugenol was evaluated in the CNS of rats. Blood, brain and spinal cord samples were collected at selected time points following eugenol administration and concentrations were determined by tandem liquid chromatography-mass spectrometry. Brain-to-plasma and spinal cord-to-plasma ratios (3.3 and 6.7, respectively) suggest that eugenol penetrates relatively well the CNS of rats, with a preferential distribution in the spinal cord. Following the induction of neuropathic pain in rats using the sciatic nerve ligation model, intrathecal injections of eugenol were done to evaluate the central effect of eugenol. Treatment with 50 μg of eugenol significantly decreased secondary mechanical allodynia after 15 min, 2 h and 4 h (p < 0.05; <0.005; <0.05, respectively) and improved thermal hyperalgesia after 2 h and 4 h (p < 0.001 and p < 0.05). The results support the hypothesis that eugenol may alleviate neuropathic pain, both allodynia and hyperalgesia, by acting centrally most probably at the level of the dorsal horn of the spinal cord where vanilloid receptors can be found.

Characterizing the effects of Eugenol on neuronal ionic currents and hyperexcitability

“…EUGL eugenolol, EUGD eugenodilol this study is about 1 μM. A recent report (Lionnet et al 2010) showed that there was a high ratio of brain-to-plasma and spinal cord-to-plasma, suggesting that EUG can penetrate the brain well. The anti-epileptic effect of EUG observed in this study may occur at a concentration achievable in humans.…”

TRP Channels Involved in Spontaneous L-Glutamate Release Enhancement in the Adult Rat Spinal Substantia Gelatinosa

“…Ohkubo and Shibata [100] have shown that eugenol inhibits formalin-induced nociceptive responses in mice. Furthermore, eugenol alleviated neuropathic pain in sciatic nerve ligation rat models [101]. A similar alleviation was produced by the oral administration of eugenol [102].…”

Effects of Eugenol on T-type Ca2+ Channel Isoforms

“…In rat models, the agent has been demonstrated to be effective in relieving pain from orofacial regions and other peripheral regions (Park et al, 2009;Lionnet et al, 2010;Yeon et al, 2011). For example, Park and his colleagues showed that subcutaneous injection of eugenol into the left vibrissa pad dose-dependently decreased the latency time of head withdrawal in response to thermal stimuli and application of eugenol onto inferior alveolar nerve reduced jaw-opening reflex in response to noxious electrical stimulation to anterial tooth pulp.…”