• S Falk, S D Schwab, M Frøsig-Jørgensen, R P Clausen, A H Dickenson, and A-M Heegaard.
• Department of Drug Design and Pharmacology, University of Copenhagen, Universitetsparken 2, 2100 Copenhagen, Denmark. Electronic address: falk@sund.ku.dk.
• Neuroscience. 2015 Apr 16;291:93-105.

AbstractPain is a common and debilitating complication for cancer patients significantly compromising their quality of life. Cancer-induced bone pain involves a complex interplay of molecular events, including mechanisms observed in inflammatory and neuropathic pain states, but also changes unique for cancer-induced bone pain. The P2X7 receptor (P2X7R) is involved in a variety of cellular functions and has been linked to both inflammatory and neuropathic pain. Here we study the analgesic potential of P2X7R antagonism in a rat model of cancer-induced bone pain. In cancer-bearing animals, the P2X7R antagonist A839977 attenuated dorsal horn neuronal responses in a modality and intensity-specific way. Spinal application of 0.4-mg/kg and 1.2-mg/kg A839977 significantly reduced the evoked responses to high-intensity mechanical and thermal stimulation, whereas no effect was seen in response to low-intensity or electrical stimulation. In contrast, A839977 had no effect on the tested parameters in naïve or sham animals. In awake animals, 40-mg/kg A839977 (i.p.) significantly reduced both early- and late-stage pain behavior. In contrast, no effect was observed in sham or vehicle-treated animals. The results suggest that the P2X7R is involved in the mechanisms of cancer-induced bone pain, and that P2X7R antagonism might be a useful analgesic target. No effect was observed in sham or naïve animals, indicating that the P2X7R-mediated effect is state-dependent, and might therefore be an advantageous target compared to traditional analgesics.Copyright © 2015 IBRO. Published by Elsevier Ltd. All rights reserved.

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