Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
5738787 | Neuroscience Letters | 2017 | 6 Pages |
â¢Constriction of the trigeminal nerve induces early heat and late tactile facial hypersensitivity.â¢CCI-ION induced spontaneous pain emerges between 5 and 15 days post injury.â¢Descending pain facilitatory pain pathways mediate evoked and spontaneous pain 15 but not 5 days post-CCI-ION.â¢Targeting RVM facilitatory pathways may improve treatment of chronic trigeminal neuropathic pain.
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 5Â days post-surgery was reversed by systemic, but not RVM lidocaine. CCI-ION-induced tactile hypersensitivity observed 15Â 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 15Â 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 15Â 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.