Original Paper

Neurochemical Research

, Volume 33, Issue 10, pp 2151-2158

Behavioral and Electrophysiological Evidence for the Differential Functions of TRPV1 at Early and Late Stages of Chronic Inflammatory Nociception in Rats

  • Hao LuoAffiliated withNeuroscience Research Institute, Peking University
  • , Isabella Shi XuAffiliated withNeuroscience Research Institute, Peking University
  • , Yi ChenAffiliated withNeuroscience Research Institute, Peking University
  • , Fei YangAffiliated withNeuroscience Research Institute, Peking University
  • , Lu YuAffiliated withNeuroscience Research Institute, Peking University
  • , Guang-Xin LiAffiliated withNeuroscience Research Institute, Peking University
  • , Feng-Yu LiuAffiliated withNeuroscience Research Institute, Peking University
  • , Guo-Gang XingAffiliated withNeuroscience Research Institute, Peking University
  • , Yu-Shun ShiAffiliated withNeuroscience Research Institute, Peking University
    • , Tan LiAffiliated withNeuroscience Research Institute, Peking University
    • , Ji-Sheng HanAffiliated withNeuroscience Research Institute, Peking University
    • , You WanAffiliated withNeuroscience Research Institute, Peking UniversityDepartment of Neurobiology, School of Basic Medical Science, Peking UniversityThe Key Laboratory for Neuroscience, The Ministry of Education, The Ministry of Public Health, Peking University Email author 

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Abstract

We previously reported that vanilloid receptor type 1 (VR1, or TRPV1) was up-regulated in dorsal root ganglion (DRG) and the spinal dorsal horn after chronic inflammatory pain produced by complete Freund’s adjuvant (CFA) injection into the plantar of rat hind paw. In the present study, we found that subcutaneous or intrathecal application of capsazepine (CPZ), a TRPV1 competitive antagonist, could inhibit thermal hyperalgesia on day 1 and on day 14 but not on day 28 after CFA injection. With extracellular electrophysiological recording, the effect of CPZ on noxious electrical or heat stimulation evoked responses of wide dynamic range (WDR) neurons in the deep layers of the spinal dorsal horn was evaluated. Under noxious electrical stimulation to sciatic nerve, CPZ applied to the spinal cord produced an inhibition on Aδ- and C-fiber evoked responses of WDR neurons on day 1 and 14, but not on day 28. Under radiant heat stimulation to the receptive field skin, subcutaneous application of CPZ significantly inhibited the background activity and extended the response latency of WDR neurons on day 14. These results provide new evidence for the functional significance of TRPV1 at the early stage, but not the late stage, in the rat model of CFA-induced inflammatory pain.

Keywords

TRPV1 Chronic pain Dorsal root ganglion Wide dynamic range neuron Spinal dorsal horn