A2A adenosine receptor regulates glia proliferation and pain after peripheral nerve injury

Peripheral nerve injury produces a persistent neuropathic pain state characterized by spontaneous pain, allodynia and hyperalgesia In this study, we evaluated the possible involvement of A(2A)Rs in the development of neuropathic pain and the expression of microglia and astrocytes in the spinal cord after sciatic nerve injury. For this purpose, partial ligation of the sciatic nerve was performed in A(2A) knockout mice and wild-type littermates. The development of mechanical and thermal allodynia, as well as thermal hyperalgesia was evaluated by using the von Frey filament model, the cold-plate test and the plantar test, respectively. In wild-type animals, sciatic nerve injury led to a neuropathic pain syndrome that was revealed in these three nociceptive behavioral tests. However, a significant decrease of the mechanical allodynia and a suppression of thermal hyperalgesia and allodynia were observed in A(2A)R deficient mice. The expression of microglia and astrocytes was enhanced in wild-type mice exposed to sciatic nerve injury and this response was attenuated in knockout animals. Taken together, our results demonstrate the involvement of A(2A)Rs in the control of neuropathic pain and propose this receptor as an interesting target for the development of new drugs for the management of this clinical syndrome (C) 2008 International Association for the Study of Pain. Published by Elsevier B.V. All rights reserved.