Electroacupuncture-Induced Dynamic Processes of Gene Expression Levels of Endogenous Opioid Peptide Precursors and Opioid Receptors in the CNS of Goats

Li-Li Cheng,Zheng-Ying Qiu,Dong-Ming Liu,Zahir Shah,Jia Wei,Yi-Qiang Wu,Ming-Xing Ding,Jian-Guo Chen,Qiong Wang,Man-Li Hu,Chang-Min Hu

doi:10.1155/2013/257682

Abstract

In order to investigate the dynamic processes of mRNA levels of proenkephalin, proopiomelanocortin, prodynorphin, and opioid receptors (δ-, μ-, and κ-receptor) induced by electroacupuncture (EA) in the central nerve system, goats were stimulated by EA of 60 Hz for 0.5 h at a set of Baihui, Santai, Ergen, and Sanyangluo points. The pain threshold was measured using the method of potassium iontophoresis. The mRNA levels of the three opioid peptide precursors and three opioid receptors were determined with quantitative real-time PCR and the levels of Met-enkephalin with SABC immunohistochemistry at 0.5 h before and at 0, 2, 4, 6, 8, 12, and 24 h after EA. The results showed that the pain threshold correlated (P < 0.01) with Met-enkephalin immunoactivities in the measured nuclei and areas of goats. The analgesic aftereffect lasted for 12 h at least. The mRNA levels of the three opioid peptide precursors and three opioid receptors began to increase at 0 h, reached the peak during the time from 4 h to 6 h or at 12 h, and remained higher at 24 h after EA was discontinued. These results suggested that the initiation of gene expression of opioid peptides and the three receptors may be associated with EA-induced analgesic aftereffect.

Highlights

Electroacupuncture (EA) is a modern version of acupuncture and extensively used in the clinic practice because it has better analgesic effect and its stimulation can be objectively quantified and controlled [1]
Studies showed that analgesia induced by EA was involved in modulations of neurotransmitters in the central nerve system (CNS) [5]
The peak of the pain threshold lagged behind that of each endogenous opioid peptides (EOPs) mRNAs. These results suggested that the initiation of gene expression of the three precursors contributed to the change in pain threshold after acupuncture termination, that is, the analgesic aftereffect

Summary

Introduction

Electroacupuncture (EA) is a modern version of acupuncture and extensively used in the clinic practice because it has better analgesic effect and its stimulation can be objectively quantified and controlled [1]. Since the 1960s, many scientists have investigated the mechanism by which electroacupuncture induces analgesic effect. Studies showed that analgesia induced by EA was involved in modulations of neurotransmitters (serotonin, acetylcholine, catecholamine, etc.) in the central nerve system (CNS) [5]. Studies verified that neuromodulators, especially some endogenous opioid peptides (enkephalin, βendorphin, and dynorphin), played a more important role in EA-induced analgesia. EA can promote the release of different endogenous opioid peptides (EOPs) which act on their corresponding receptors (δ-, μ-, or κ-receptor) to exert analgesic effect [6,7,8,9]

Methods

Results

Discussion

Conclusion