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Long-term synaptic plasticity in the spinal dorsal horn and its modulation by electroacupuncture in rats with neuropathic pain.
Exp Neurol. 2007 Dec; 208(2):323-32.EN

Abstract

Our previous study has reported that electroacupuncture (EA) at low frequency of 2 Hz had greater and more prolonged analgesic effects on mechanical allodynia and thermal hyperalgesia than that EA at high frequency of 100 Hz in rats with neuropathic pain. However, how EA at different frequencies produces distinct analgesic effects on neuropathic pain is unclear. Neuronal plastic changes in spinal cord might contribute to the development and maintenance of neuropathic pain. In the present study, we investigated changes of spinal synaptic plasticity in the development of neuropathic pain and its modulation by EA in rats with neuropathic pain. Field potentials of spinal dorsal horn neurons were recorded extracellularly in sham-operated rats and in rats with spinal nerve ligation (SNL). We found for the first time that the threshold for inducing long-term potentiation (LTP) of C-fiber-evoked potentials in dorsal horn was significantly lower in SNL rats than that in sham-operated rats. The threshold for evoking the C-fiber-evoked field potentials was also significantly lower, and the amplitude of the field potentials was higher in SNL rats as compared with those in the control rats. EA at low frequency of 2 Hz applied on acupoints ST 36 and SP 6, which was effective in treatment of neuropathic pain, induced long-term depression (LTD) of the C-fiber-evoked potentials in SNL rats. This effect could be blocked by N-methyl-d-aspartic acid (NMDA) receptor antagonist MK-801 and by opioid receptor antagonist naloxone. In contrast, EA at high frequency of 100 Hz, which was not effective in treatment of neuropathic pain, induced LTP in SNL rats but LTD in sham-operated rats. Unlike the 2 Hz EA-induced LTD in SNL rats, the 100 Hz EA-induced LTD in sham-operated rats was dependent on the endogenous GABAergic and serotonergic inhibitory system. Results from our present study suggest that (1) hyperexcitability in the spinal nociceptive synaptic transmission may occur after nerve injury, which may contribute to the development of neuropathic pain; (2) EA at low or high frequency has a different effect on modulating spinal synaptic plasticities in rats with neuropathic pain. The different modulation on spinal LTD or LTP by low- or high-frequency EA may be a potential mechanism of different analgesic effects of EA on neuropathic pain. LTD of synaptic strength in the spinal dorsal horn in SNL rats may contribute to the long-lasting analgesic effects of EA at 2 Hz.

Authors+Show Affiliations

Department of Neurobiology, Key Laboratory for Neuroscience of the Ministry of Education and Public Health, Peking University, 38 Xue-Yuan Road, Beijing 100083, People's Republic of China. ggxing@bjmu.edu.cnNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

17936754

Citation

Xing, Guo-Gang, et al. "Long-term Synaptic Plasticity in the Spinal Dorsal Horn and Its Modulation By Electroacupuncture in Rats With Neuropathic Pain." Experimental Neurology, vol. 208, no. 2, 2007, pp. 323-32.
Xing GG, Liu FY, Qu XX, et al. Long-term synaptic plasticity in the spinal dorsal horn and its modulation by electroacupuncture in rats with neuropathic pain. Exp Neurol. 2007;208(2):323-32.
Xing, G. G., Liu, F. Y., Qu, X. X., Han, J. S., & Wan, Y. (2007). Long-term synaptic plasticity in the spinal dorsal horn and its modulation by electroacupuncture in rats with neuropathic pain. Experimental Neurology, 208(2), 323-32.
Xing GG, et al. Long-term Synaptic Plasticity in the Spinal Dorsal Horn and Its Modulation By Electroacupuncture in Rats With Neuropathic Pain. Exp Neurol. 2007;208(2):323-32. PubMed PMID: 17936754.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Long-term synaptic plasticity in the spinal dorsal horn and its modulation by electroacupuncture in rats with neuropathic pain. AU - Xing,Guo-Gang, AU - Liu,Feng-Yu, AU - Qu,Xiao-Xiu, AU - Han,Ji-Sheng, AU - Wan,You, Y1 - 2007/09/12/ PY - 2007/03/18/received PY - 2007/08/31/revised PY - 2007/09/04/accepted PY - 2007/10/16/pubmed PY - 2008/2/1/medline PY - 2007/10/16/entrez SP - 323 EP - 32 JF - Experimental neurology JO - Exp Neurol VL - 208 IS - 2 N2 - Our previous study has reported that electroacupuncture (EA) at low frequency of 2 Hz had greater and more prolonged analgesic effects on mechanical allodynia and thermal hyperalgesia than that EA at high frequency of 100 Hz in rats with neuropathic pain. However, how EA at different frequencies produces distinct analgesic effects on neuropathic pain is unclear. Neuronal plastic changes in spinal cord might contribute to the development and maintenance of neuropathic pain. In the present study, we investigated changes of spinal synaptic plasticity in the development of neuropathic pain and its modulation by EA in rats with neuropathic pain. Field potentials of spinal dorsal horn neurons were recorded extracellularly in sham-operated rats and in rats with spinal nerve ligation (SNL). We found for the first time that the threshold for inducing long-term potentiation (LTP) of C-fiber-evoked potentials in dorsal horn was significantly lower in SNL rats than that in sham-operated rats. The threshold for evoking the C-fiber-evoked field potentials was also significantly lower, and the amplitude of the field potentials was higher in SNL rats as compared with those in the control rats. EA at low frequency of 2 Hz applied on acupoints ST 36 and SP 6, which was effective in treatment of neuropathic pain, induced long-term depression (LTD) of the C-fiber-evoked potentials in SNL rats. This effect could be blocked by N-methyl-d-aspartic acid (NMDA) receptor antagonist MK-801 and by opioid receptor antagonist naloxone. In contrast, EA at high frequency of 100 Hz, which was not effective in treatment of neuropathic pain, induced LTP in SNL rats but LTD in sham-operated rats. Unlike the 2 Hz EA-induced LTD in SNL rats, the 100 Hz EA-induced LTD in sham-operated rats was dependent on the endogenous GABAergic and serotonergic inhibitory system. Results from our present study suggest that (1) hyperexcitability in the spinal nociceptive synaptic transmission may occur after nerve injury, which may contribute to the development of neuropathic pain; (2) EA at low or high frequency has a different effect on modulating spinal synaptic plasticities in rats with neuropathic pain. The different modulation on spinal LTD or LTP by low- or high-frequency EA may be a potential mechanism of different analgesic effects of EA on neuropathic pain. LTD of synaptic strength in the spinal dorsal horn in SNL rats may contribute to the long-lasting analgesic effects of EA at 2 Hz. SN - 0014-4886 UR - https://www.unboundmedicine.com/medline/citation/17936754/Long_term_synaptic_plasticity_in_the_spinal_dorsal_horn_and_its_modulation_by_electroacupuncture_in_rats_with_neuropathic_pain_ L2 - https://linkinghub.elsevier.com/retrieve/pii/S0014-4886(07)00338-X DB - PRIME DP - Unbound Medicine ER -