Role of peptidergic neurons in modulating acupoint sensitization caused by neck acute inflammatory pain in rats 肽能神经元对颈部急性炎性痛模型大鼠穴位敏化的调节作用

Abstract

Objective

Pain is a health problem frequently reported in the clinical and general populations. Acupoint therapy is one of the most effective ways to treat pain; however, its mechanism remains unclear. Therefore, this study aimed to explore the relationship between distal acupoints, dorsal root ganglion (DRG) neurons, and spinal cord dorsal horn (SDH) neurons in neck acute inflammatory pain (NAIP).

Methods

NAIP model rats were used to explore the relationship between acupoint sensitization and pain. Out of fourteen rats, ten rats were grouped into control and NAIP groups, five rats in control and five rats in NAIP. Mustard oil was subcutaneously injected on one side between the C4 and C7 vertebrae of the neck to establish an NAIP model. Evans blue (EB) was injected through the tail vein to detect sensitized acupoints after NAIP modeling. EB exudation in the body, Lieque (LU7), and Lingdao (HT4) were evaluated. An immunofluorescence assay was conducted to detect the expression of calcitonin gene-related peptide (CGRP), isolectin B4 (IB4), and c-Fos in the dorsal root ganglion (DRG) and spinal cord dorsal medullae spinalis (CDMS). Four rats were used for the retrograde labeling of neurons of the LU7 region to the DRG and CDMS using CTB-488 and CTB-555 microinjection.

Results

NAIP was shown to lead to oozing and pain sensitization in the LU7 and HT4 and increased the proportion of c-Fos⁺/CGRP⁺ and c-Fos⁺/IB4⁺ cells in both the DRG and CDMS. CTB-488 and CTB-555 injected into the LU7 and sensitization point areas were observed in the DRG and CDMS regions of NAIP rats.

Conclusions

Our study revealed that NAIP could lead to oozing and pain sensitization in the LU7 and HT4 regions and that the pain point around LU7 might result from the transfer of peptidergic (CGRP-positive) and non-peptidergic (IB4-positive) neurons in the DRG and CDMS.