@article{oai:nagasaki-u.repo.nii.ac.jp:00018206,
 author = {Matsumoto, Misaki and Xie, Weijiao and Ma, Lin and Ueda, Hiroshi},
 issue = {25},
 journal = {Molecular Pain},
 month = {Jul},
 note = {Background: We have previously demonstrated that different spinal transmissions are involved in the nociceptive behavior caused by electrical stimulation of Aβ-, Aδ- or C-fibers using a Neurometer? in na?ve mice. In this study, we attempted to pharmacologically characterize the alteration in spinal transmission induced by partial sciatic nerve injury in terms of nociceptive behavior and phosphorylation of extracellular signal-regulated kinase (pERK) in the spinal dorsal horn.  Results: Aβ-fiber responses (2000-Hz), which were selectively blocked by the AMPA/kainate antagonist CNQX in na?ve mice, were hypersensitized but blocked by the NMDA receptor antagonists MK-801 and AP-5 in injured mice in an electrical stimulation-induced paw withdrawal (EPW) test. Although Aδ-fiber responses (250-Hz) were also hypersensitized by nerve injury, there was no change in the pharmacological characteristics of Aδ-fiber responses through NMDA receptors. On the contrary, C-fiber responses (5-Hz) were hyposensitized by nerve injury. Moreover, Aδ- and C-, but not Aβ-fiber stimulations significantly increased the number of pERK-positive neurons in the superficial spinal dorsal horns of na?ve mice, and corresponding antagonists used in the EPW test inhibited this increase. In mice with nerve injury, Aβ- as well as Aδ-fiber stimulations significantly increased the number of pERK-positive neurons in the superficial spinal dorsal horn, whereas C-fiber stimulation decreased this number. The nerve injury-specific pERK increase induced by Aβ-stimulation was inhibited by MK-801 and AP-5, but not by CNQX. However, Aβ- and Aδ-stimulations did not affect the number or size of pERK-positive neurons in the dorsal root ganglion, whereas C-fiber-stimulation selectively decreased the number of pERK-positive neurons.  Conclusion: These results suggest that Aβ-fiber perception is newly transmitted to spinal neurons, which originally receive only Aδ- and C-fiber-mediated pain transmission, through NMDA receptor-mediated mechanisms, in animals with nerve injury. This pharmacological switch in Aβ-fiber spinal transmission could be a mechanism underlying neuropathic allodynia., Molecular Pain, 4, 25; 2008},
 pages = {1--12},
 title = {Pharmacological switch in Aβ-fiber stimulation-induced spinal transmission in mice with partial sciatic nerve injury},
 volume = {4},
 year = {2008}
}