The efficacy of frequency-specific acupuncture stimulation on extracellular dopamine concentration in striatum--a rat model study.

Acupuncture is a practice that has existed in Chinese society for thousands of years. Today, it is gaining greater acceptance and integration into medical practices of the western world. Its mechanism, however, remains elusive. Our study shows that only specific stimulation frequencies at specific acupoints will induce dopamine release in the corpus striatum, as demonstrated by in vivo microdialysis performed on Sprague-Dawley rats. In the first trial, electroacupuncture (EA) stimulation at 15 Hz and 15 mA was conducted at six different points on the upper limbs of the experimental rats. These points mimic acupoints along six different meridians in the human body. Only Point 2 (corresponding to Pericardium 7) induced a response. In the second trial, EA stimulation at varying frequencies of 3, 6, 9, 12, 15, 18, 21, 24, 27 and 30 Hz, and 15 mA were conducted through Point 2. Stimulation at 6 and 15 Hz induced an immediate response; 21 Hz induced a response only after the ceasing of stimulation. All other frequencies failed to induce a response. The data point to the importance of frequency-specific stimulation at specific acupoints for the release of neurotransmitters in the brain. We speculate that each meridian entails a stimulus of a specific frequency and intensity, which induces the release of its associated neurotransmitters or cytokines. This is a concept with far-reaching clinical implications for acupuncture therapy, including the treatment of dopamine-related disorders.