Descending facilitatory pain pathways mediate ongoing pain and tactile hypersensitivity in a rat model of trigeminal neuropathic pain

作者：Nones C F M; Claudino R F; Ferreira L E N; dos Reis R C; King T; Chichorro J G^*

来源：Neuroscience Letters, 2017, 644: 18-23.

DOI：10.1016/j.neulet.2017.02.047

• Trigeminal neuropathic pain
• RVM
• Spontaneous pain
• Hypersensitivity

The Chronic Constriction Injury of the Infraorbital Nerve (CCI-ION) is a well-established model to study facial sensory changes related to trigeminal neuropathic pain. CCI-ION induces heat hypersensitivity that resolves within 2-3 weeks and a delayed mechanical hypersensitivity that emerges during the second week post-injury. The role of descending facilitatory pain pathways from the rostro ventromedial medulla (RVM) in mediating the heat and tactile hypersensitivity was examined. CCI-ION induced heat hypersensitivity observed 5 days post-surgery was reversed by systemic, but not RVM lidocaine. CCI-ION-induced tactile hypersensitivity observed 15 days post-surgery was reversed by systemic lidocaine and attenuated by RVM lidocaine. CCI-ION-induced spontaneous pain was determined using conditioned place preference (CPP) to pain relief at each time-point. At day 5 post-CCI-ION, neither systemic nor RVM lidocaine induced CPP. However, at 15 days post-CCI-ION, CPP was observed to the chamber paired with RVM lidocaine, but not systemic lidocaine. These data indicate that CCI-ION induced heat hypersensitivity is not dependent on descending facilitatory pain pathways 5-days post-injury whereas descending facilitatory pain pathways mediate tactile allodynia and spontaneous pain 15 days post-CCI-ION. This suggests that CCI-ION induces early peripheral sensitization followed by development of central sensitization that mediates spontaneous pain and contributes to mechanical hypersensitivity.

• 出版日期2017-3-22