Peer-Reviewed Research: Exploring the Role of Nitric Oxide and cGMP in Acupuncture Points: A Modern Scientific Analysis
The paper titled "Responses of nitric oxide-cGMP releases in acupuncture point to electroacupuncture in human skin in vivo using dermal microdialysis" by Nainn-Tsyr Jou and Sheng-Xing Ma explores the physiological effects of electroacupuncture (EA) on the pericardium (PC) acupuncture points in human skin. Specifically, it examines how EA modulates the release of nitric oxide (NO) and cyclic guanosine monophosphate (cGMP) at acupuncture points compared to non-meridian control areas, using dermal microdialysis. This research provides valuable insights into the biochemical processes that might contribute to the therapeutic effects of acupuncture in improving local microcirculation.
Summary of the Study
Objective
The primary objective of the study was to investigate whether EA stimulation of the PC 3 acupoint affects the release of NO and cGMP at the PC 4 acupoint in comparison to a non-meridian control area. The authors hypothesized that EA would increase NO and cGMP release, which would reflect enhanced local microcirculation and the physiological effects of acupuncture.
Methods
The researchers employed dermal microdialysis to measure NO and cGMP in human volunteers, a method that allows real-time monitoring of molecular changes in the skin’s interstitial fluid. The experiment was conducted with 24 healthy volunteers between the ages of 18 and 58. The study included three experimental groups:
PC 4 dialysis without EA (control group)
Non-meridian area dialysis with EA stimulation at PC 3
PC 4 dialysis with EA stimulation at PC 3
For the EA groups, a mild electrical pulse (5 volts at 10 Hz) was applied to the PC 3 acupoint for 15 minutes. NO was measured as the sum of nitrite and nitrate concentrations (NOx-), and cGMP levels were determined through enzyme-linked immunosorbent assay (ELISA). Data were collected before, during, and after EA treatment, and statistical analyses were performed using one-way ANOVA and Student’s t-tests.
Results
The study found several key outcomes:
Baseline Concentrations: Both NOx- and cGMP baseline levels were higher at the PC 4 acupoint compared to the non-meridian area, suggesting a physiological difference between acupoints and non-acupuncture sites.
NOx- Reduction Attenuation: NOx- concentrations generally decreased over time during the 120-minute microdialysis procedure. However, the reduction in NOx- was significantly attenuated at the PC 4 acupoint during and after EA stimulation at PC 3. This effect was not observed at the non-meridian area, indicating that the EA-induced NO release was acupoint-specific.
Increased cGMP: cGMP concentrations increased significantly at the PC 4 acupoint following EA stimulation. This was consistent with the observed increase in NO release, as NO is known to stimulate cGMP production, which plays a role in vasodilation and other physiological processes.
Timing of Effects: The most notable increase in NO release occurred between 20 to 40 minutes after EA stimulation, suggesting a time-dependent response to acupuncture. NO release returned to baseline levels 60 to 80 minutes after stimulation, highlighting the transient nature of EA’s effects on local microcirculation.
Discussion
The study provides compelling evidence that EA can enhance NO and cGMP release at specific acupuncture points, supporting the hypothesis that acupuncture induces localized physiological changes that may contribute to its therapeutic effects. The increased NO release, in particular, is significant because NO is a well-known vasodilator that improves blood flow and may help alleviate conditions involving poor circulation or inflammation. The parallel increase in cGMP further suggests that the NO-cGMP signaling pathway is actively involved in the acupuncture-induced microcirculation improvement.
Acupoint Specificity
One of the most critical findings of this study is the specificity of the NO and cGMP responses to acupuncture points. The fact that these effects were observed at PC 4 but not at the non-meridian control area reinforces the traditional Chinese medicine (TCM) concept that acupoints possess unique physiological properties. Acupuncture’s ability to modulate NO and cGMP levels specifically at these points may explain, in part, how it achieves its therapeutic effects in clinical practice.
Mechanism of Action
The study provides insights into the biochemical mechanisms underlying acupuncture’s effects, suggesting that the increased NO release at acupuncture points might be due to the rich distribution of neural and vascular structures at these locations. The authors propose that NO synthase, particularly neuronal and endothelial NO synthase, may be activated by EA, leading to increased NO production. This, in turn, triggers the production of cGMP, which further promotes vasodilation and local blood flow.
Strengths and Limitations
Strengths
The use of dermal microdialysis offers a non-invasive method to directly measure molecular changes in the skin, providing real-time data on acupuncture’s physiological effects.
The study’s randomized and blinded design strengthens the reliability of the results.
The focus on acupoint specificity is a valuable contribution to acupuncture research, helping to clarify how acupuncture works at a biochemical level.
Limitations
The study’s sample size is relatively small, which may limit the generalizability of the results.
The study focused on a single acupuncture point (PC 3) and a single meridian (pericardium), so it remains unclear whether these findings would extend to other acupoints or meridians.
The transient nature of the observed effects raises questions about the long-term clinical relevance of the findings. Further research is needed to determine whether repeated EA treatments produce cumulative effects on NO and cGMP release.
Conclusion
This study provides valuable evidence supporting the hypothesis that EA induces localized NO and cGMP release at acupuncture points, which may contribute to its therapeutic effects. The findings are consistent with the traditional Chinese medicine concept of acupoint specificity, demonstrating that acupuncture can selectively modulate biochemical processes that improve microcirculation. Further research with larger sample sizes and additional acupoints is necessary to fully understand the mechanisms by which acupuncture achieves its clinical benefits.
Reference
Jou, N-T., & Ma, S-X. (2009). Responses of nitric oxide-cGMP releases in acupuncture point to electroacupuncture in human skin in vivo using dermal microdialysis. Microcirculation, 16(5), 434–443
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