Abstract
The aim of this study was to investigate the analgesic mechanism of electroacupuncture (EA) in the treatment of neuropathological pain. A total of 60 Sprague-Dawley rats were randomly divided into three groups, namely the spinal nerve ligation (SNL), electroacupuncture (SNL + EA) and normal control groups, with 20 rats in each group. The up-down method was used to determine the bipedal 50% mechanical paw withdrawal threshold (PWT). The ultrastructure of the injured-side L5 nerve root (n=6) was observed by electron microscopy. The mRNA levels of brain-derived neurotrophic factor (BDNF) and purinergic receptor P2X, ligand-gated ion channel 4 (P2X4) in the spinal cord (n=14) were determined by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). The postoperative PWT of the injured-side hindpaw in the SNL group at each time point was lower than that in the control group (P<0.01); there were differences of statistical significance between the PWT values of the SNL + EA and SNL groups on postoperative days 14 and 21 (P<0.05). Postoperatively, the PWT of the hindpaw on the uninjured-side was significantly lower in the SNL group when compared with that of the control group on days 10, 14 and 21 (P<0.05). Following the EA treatment, axonal demyelination was reduced and vascular proliferation was observed within the visual field. In addition, following the EA treatment, BDNF expression levels in the spinal dorsal horn increased (P<0.05), while the expression of P2X4 was not different from that in the SNL group. EA exerted an analgesic effect on the SNL model in a time-dependent manner, and improved the blood supply to the nerve root. Following the EA treatment, the expression of P2X4 did not change significantly compared with that in the SNL group, whereas the spinal secretion of BDNF increased. However, the exact mechanism requires further study.
Highlights
The spinal nerve ligation model (SNL) was first proposed by Kim and Chung in 1992 [1]
Studies have shown that when neuropathological pain (NP) occurs, the spinal levels of purinergic receptor P2X, ligand-gated ion channel 4 (P2X4) and microglial levels of brain‐derived neurotrophic factor (BDNF) play important roles in the generation and maintenance of NP [4,5]; it remains unclear whether EA affects the spinal expression of P2X4 and BDNF in SNL model rats during analgesia
The results of this study demonstrated that compared with the preoperative baseline value, the postoperative 50% paw withdrawal threshold (PWT) in the SNL group decreased progressively, and the hyperalgesia was significant, indicating that the SNL modeling was successfully established
Summary
The spinal nerve ligation model (SNL) was first proposed by Kim and Chung in 1992 [1]. Studies have shown that when NP occurs, the spinal levels of purinergic receptor P2X, ligand-gated ion channel 4 (P2X4) and microglial levels of brain‐derived neurotrophic factor (BDNF) play important roles in the generation and maintenance of NP [4,5]; it remains unclear whether EA affects the spinal expression of P2X4 and BDNF in SNL model rats during analgesia. The up-down method was used to measure the bipedal 50% mechanical paw withdrawal threshold (PWT), electron microscopy was used to observe the ultrastructure of the injured-side L5 nerve root (n=6) and reverse transcription‐quantitative polymerase chain reaction (RT-qPCR) was performed to detect the mRNA levels of BDNF and P2X4 in the spinal cord. The aim of the study was to investigate the relationship between analgesia and repair, and provide a theoretical basis for the mechanism of EA‐induced analgesia
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