• Shu-Mei Chen, Mao-Hsien Wang, Hung-Sheng Soung, Hsiang-Chien Tseng, Chih-Hsiang Fang, Yi-Wen Lin, Chih-Chuan Yang, and Cheng-Chia Tsai.
• Department of Neurosurgery, Taipei Medical University Hospital, Taipei Medical University, Taipei, 110, Taiwan, ROC; Department of Surgery, School of Medicine, Taipei Medical University, Taipei, 110, Taiwan, ROC.
• J Formos Med Assoc. 2022 Apr 1; 121 (4): 802-814.

Background/PurposeWe investigated the protective efficacy of l-theanine (LT), the major amino acid components of green tea, on chronic constriction injury (CCI) of sciatic nerve-induced neuropathic pain (NP) development and neuronal functional changes in rats.MethodsRats with NP induced by CCI of the left sciatic nerve and sham-operated rats received LT or saline solution, with pain sensitive tests of thermal hyperalgesia and mechanical allodynia. Motor and sensory nerve conduction velocities were measured after surgery. Subsequently, the rats were sacrificed; the sciatic nerve was excised, homogenized, prepared and subjected for estimation of nitric oxide (NO), malondialdehyde (MDA), glutathione (GSH), superoxide dismutase (SOD), catalase (CAT), tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), interleukin-6 (IL-6), myeloperoxidase (MPO), and caspase-3.ResultsCCI produced a significant increase in hyperalgesia and allodynia, an increase in SFI, a decrease in nerve conduction velocity, increases in NO, MDA, TNF-α, IL-1β, IL-6, MPO, and caspase-3 levels, as well as reduction of GSH, SOD, and CAT in the rat sciatic nerve. LT treatment significantly and dose-dependently alleviated CCI-induced nociceptive pain thresholds and ameliorated abnormal nerve conduction and functional loss in rats with CCI. Moreover, LT treatment reduced NO and MDA levels, increased antioxidative strength, and markedly suppressed the levels of neuroinflammatory and apoptotic markers in injured sciatic nerves.ConclusionThis is the first report on the ameliorative effect of LT in CCI-induced NP in rats. This effect might be attributed to its anti-oxidative, anti-inflammatory, anti-apoptotic, and neuroprotective, thus making it potentially useful as an adjuvant to conventional treatment.Copyright © 2021 Formosan Medical Association. Published by Elsevier B.V. All rights reserved.

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