• Young-Hwan Jung, Yeo Ok Kim, Jung Hyun Han, Yong-Chul Kim, and Myung Ha Yoon.
• From the *School of Life Sciences, Gwangju Institute of Science and Technology (GIST), Gwangju, Republic of Korea; †Department of Anesthesiology and Pain Medicine, Chonnam National University, Medical School, Gwangju, Republic of Korea; ‡Department of Biomedical Science and Engineering at Gwangju Institute of Science and Technology (GIST), Gwangju, Republic of Korea; and §Center for Creative Biomedical Scientists at Chonnam National University, Gwangju, Republic of Korea.
• Anesth. Analg. 2017 Aug 1; 125 (2): 670-677.

BackgroundNeuropathic pain should be treated with drug combinations exhibiting multiple analgesic mechanisms of action because the mechanism of neuropathic pain involves multiple physiological causes and is mediated by multiple pathways. In this study, we defined the pharmacological interaction of BRL52537 (κ-opioid agonist), pregabalin (calcium channel modulator), AF 353 (P2X3 receptor antagonist), and A804598 (P2X7 receptor antagonist).MethodsAnimal models of neuropathic pain were established by spinal nerve ligation (SNL) in male Sprague-Dawley rats, and responses to the mechanical stimulation using von Frey filaments were measured. Drugs were administered by intrathecal route and were examined for antiallodynic effects, and drug interactions were evaluated using isobolographic analysis. The mRNA expression levels of pain-related receptors in each spinal cord or dorsal root ganglion of naïve, SNL, and drug-treated SNL rats were evaluated using real-time polymerase chain reaction.ResultsIntrathecal BRL52537, pregabalin, AF 353, and A804598 produced antiallodynic effects in SNL rats. In the drug combination studies, intrathecal coadministration of BRL52537 with pregabalin or A804598 exhibited synergistic interactions, and other drugs combinations showed additivity. The rank order of potency was observed as follows: BRL52537 + pregabalin > BRL52537 + A804598 > pregabalin + AF 353 > A804598 + pregabalin > BRL52537 + AF 353 > AF 353 + A804598. Real-time polymerase chain reaction indicated that alterations of P2X3 receptor and calcium channel mRNA expression levels were observed, while P2X7 receptor and κ-opioid receptor expression levels were not altered.ConclusionsThese results demonstrated that intrathecal combination of BRL52537, pregabalin, AF 353, and A804598 synergistically or additively attenuated allodynia evoked by SNL, which suggests the possibility to improve the efficacy of single-drug administration.

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