RT Journal Article SR Electronic T1 Chronic Morphine-Induced Changes in Signaling at the A3 Adenosine Receptor Contribute to Morphine-Induced Hyperalgesia, Tolerance, and Withdrawal JF Journal of Pharmacology and Experimental Therapeutics JO J Pharmacol Exp Ther FD American Society for Pharmacology and Experimental Therapeutics SP 331 OP 341 DO 10.1124/jpet.120.000004 VO 374 IS 2 A1 Timothy M. Doyle A1 Tally M. Largent-Milnes A1 Zhoumou Chen A1 Vasiliki Staikopoulos A1 Emanuela Esposito A1 Rebecca Dalgarno A1 Churmy Fan A1 Dilip K. Tosh A1 Salvatore Cuzzocrea A1 Kenneth A. Jacobson A1 Tuan Trang A1 Mark R. Hutchinson A1 Gary J. Bennett A1 Todd W. Vanderah A1 Daniela Salvemini YR 2020 UL http://jpet.aspetjournals.org/content/374/2/331.abstract AB Treating chronic pain by using opioids, such as morphine, is hampered by the development of opioid-induced hyperalgesia (OIH; increased pain sensitivity), antinociceptive tolerance, and withdrawal, which can contribute to dependence and abuse. In the central nervous system, the purine nucleoside adenosine has been implicated in beneficial and detrimental actions of morphine, but the extent of their interaction remains poorly understood. Here, we demonstrate that morphine-induced OIH and antinociceptive tolerance in rats is associated with a twofold increase in adenosine kinase (ADK) expression in the dorsal horn of the spinal cord. Blocking ADK activity in the spinal cord provided greater than 90% attenuation of OIH and antinociceptive tolerance through A3 adenosine receptor (A3AR) signaling. Supplementing adenosine signaling with selective A3AR agonists blocked OIH and antinociceptive tolerance in rodents of both sexes. Engagement of A3AR in the spinal cord with an ADK inhibitor or A3AR agonist was associated with reduced dorsal horn of the spinal cord expression of the NOD-like receptor pyrin domain-containing 3 (60%–75%), cleaved caspase 1 (40%–60%), interleukin (IL)-1β (76%–80%), and tumor necrosis factor (50%–60%). In contrast, the neuroinhibitory and anti-inflammatory cytokine IL-10 increased twofold. In mice, A3AR agonists prevented the development of tolerance in a model of neuropathic pain and reduced naloxone-dependent withdrawal behaviors by greater than 50%. These findings suggest A3AR-dependent adenosine signaling is compromised during sustained morphine to allow the development of morphine-induced adverse effects. These findings raise the intriguing possibility that A3AR agonists may be useful adjunct to opioids to manage their unwanted effects.SIGNIFICANCE STATEMENT The development of hyperalgesia and antinociceptive tolerance during prolonged opioid use are noteworthy opioid-induced adverse effects that reduce opioid efficacy for treating chronic pain and increase the risk of dependence and abuse. We report that in rodents, these adverse effects are due to reduced adenosine signaling at the A3AR, resulting in NOD-like receptor pyrin domain-containing 3–interleukin-1β neuroinflammation in spinal cord. These effects are attenuated by A3AR agonists, suggesting that A3AR may be a target for therapeutic intervention with selective A3AR agonist as opioid adjuncts.