Yonsei Med J.  2011 Nov;52(6):1016-1021. 10.3349/ymj.2011.52.6.1016.

Analgesic Mechanism of Electroacupuncture in an Arthritic Pain Model of Rats: A Neurotransmitter Study

• Yoo YC
• Oh JH
• Kwon TD
• Lee YK
• Bai SJ

• KMID: 1058824
• DOI: http://doi.org/10.3349/ymj.2011.52.6.1016

Abstract

PURPOSE
We investigated what kinds of neurotransmitters are related with electroacupuncture (EA) analgesia in an arthritic pain model of rats.
MATERIALS AND METHODS
One hundred rats were assigned to six groups: control, EA, opioid, adrenergic, serotonin and dopamine group. A standardized model of inflammatory arthritis was produced by injecting 2% carrageenan into the knee joint cavity. EA was applied to an acupoint for 30 min in all groups except fo the control group. In the opioid, adrenergic, serotonin and dopamine groups, each receptor antagonist was injected intraperitoneally to their respective group before initiating EA.
RESULTS
In the opioid receptor antagonist group, adrenergic receptor antagonist group, serotonin receptor antagonist group, dopamine receptor antagonist group and the control group weight-bearing force decreased significantly from 30 min to 180 min after EA in comparison with the EA group.
CONCLUSION
The analgesic effects of EA are related to opioid, adrenergic, serotonin and dopamine receptors in an arthritic pain model of rats.

Keyword

Arthritis; electroacupuncture; neurotransmitter; pain; weight-bearing

MeSH Terms

Acupuncture Analgesia/*methods
Adrenergic Antagonists/therapeutic use
Animals
Arthritis/chemically induced/drug therapy/physiopathology/*therapy
Carrageenan/toxicity
Dopamine Antagonists/therapeutic use
Electroacupuncture/*methods
Male
Neurotransmitter Agents/*metabolism
Pain/drug therapy/metabolism
Rats
Rats, Sprague-Dawley
Receptors, Adrenergic/metabolism
Receptors, Dopamine/metabolism
Receptors, Opioid/antagonists & inhibitors/metabolism
Receptors, Serotonin/metabolism
Serotonin Antagonists/therapeutic use

Figure

• 

  Fig. 1 Effects of manual acupuncture on weight-bearing behavioral tests of rats with arthritis. Percent changes of weight-bearing force to body weight compared with responses before acupuncture were plotted. There were statistically significant differences in response between the acupuncture group and the control group at 30-180 min after the termination of acupuncture. There were no differences in response between the sham acupoint group and the control a group. Data were analyzed by one-way ANOVA with the Dunnett's (2-sided) post-hoc test for multiple comparisons. *Statistical significance was defined as p<0.05. ANOVA, analysis of variance.

• 

  Fig. 2 Effect of low frequency and high frequency electroacupuncture on weight-bearing behavioral tests of rats with arthritis. Percent changes of weight-bearing force to body weight compared with responses before electroacupuncture were plotted. There were statistically significant differences in response between the EA group and control group at 60-180 min after the termination of electroacupuncture. There were no differences in response between the sham acupoint group and the control group. Data were analyzed by one-way ANOVA with the Dunnett's (2-sided) post-hoc test for multiple comparisons. *Statistical significance was defined as p<0.05. EA, electroacupuncture; ANOVA, analysis of variance.

• 

  Fig. 3 Effect of neurotransmitter antagonists on weight bearing behavior test of rats with arthritis. Percent changes of weight-bearing force to body weight compared with responses before electroacupuncture were plotted. The neurotransmitter receptor antagonist groups and control group showed significant decrease in weight-bearing force from 30 min to 180 min after electroacupuncture in comparison with the EA group. Data were analyzed by one-way ANOVA with the Dunnett's (2-sided) post-hoc test for multiple comparisons. *Statistical significance was defined as p<0.05. EA, electroacupuncture; ANOVA, analysis of variance.

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