Changes in responses of neurons in spinal and medullary subnucleus reticularis dorsalis to acupoint stimulation in rats with visceral hyperalgesia.

Ling-Ling Yu,Qing-Guang Qin,Bing Zhu,Hui Ben,Guo-Fu Huang,Pei-Jing Rong,Liang Li

doi:10.1155/2014/768634

Abstract

The purpose of this study was to explore the mechanism of acupoints sensitization phenomenon at the spinal and medulla levels. Experiments were performed on adult male Sprague-Dawley rats and visceral noxious stimuli was generated by colorectal distension (CRD). The activities of wide dynamic range (WDR) and subnucleus reticularis dorsalis (SRD) neurons were recorded. The changes of the reactions of WDR and SRD neurons to electroacupuncture (EA) on acupoints of “Zusanli-Shangjuxu” before and after CRD stimulation were observed. The results showed that visceral nociception could facilitate the response of neurons to acupoints stimulation. In spinal dorsal horn, EA-induced activation of WDR neurons further increased to 106.84 ± 17.33% (1.5 mA) (P < 0.001) and 42.27 ± 13.10% (6 mA) (P < 0.01) compared to the neuronal responses before CRD. In medulla oblongata, EA-induced activation of SRD neurons further increased to 63.28 ± 15.96% (1.5 mA) (P < 0.001) and 25.02 ± 7.47% (6 mA) (P < 0.01) compared to that before CRD. Taken together, these data suggest that the viscerosomatic convergence-facilitation effect of WDR and SRD neurons may underlie the mechanism of acupoints sensitization. But the sensitizing effect of visceral nociception on WDR neurons is stronger than that on SRD neurons.

Highlights

Due to different structural function units of related somites, there exist specific relationships between acupoints and target organs
Most of the wide dynamic range (WDR) neurons were located in laminas IV and V, and a few in laminas I and VI of the gray matter marked by electrophoresis of the pontamine sky blue dye at the end of experiment (see Figure 1(a))
28 subnucleus reticularis dorsalis (SRD) neurons were recorded in the dorsal medulla and their positions were mapped by electrophoretic deposition of pontamine sky blue at the end of experiments

Summary

Introduction

Due to different structural function units of related somites, there exist specific relationships between acupoints and target organs. Clinical studies have shown that the pressure-pain threshold of related acupoints decreases in patients with functional intestinal disorder [2] and gastric ulcer [3]. These findings suggest that acupoint is a dynamic functional unit and can be sensitized when viscera is under pathological process. Many studies have shown that referred pain often occurs in body regions somatotopically different from the sites of target organs [9, 10] and has segmental pattern related to target organs [11], suggesting the involvement of central hyperalgesic mechanisms [12]. Our working hypothesis is that central sensitization produce the increased pain sensitivity in sensitized acupoints

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Conclusion