Autonomic nerve effects of acupuncture stimulations to abdomen detected by analysis of heart rate variability

Acupuncture has been widely used for normalizing autonomic functions in various systems; however, there is only limited evidence on its effects on objective autonomic indexes. The aim of this study was to investigate the autonomic nerve effects of acupuncture stimulations to the abdomen by an analysis of heart rate variability (HRV). In 12 healthy volunteers, beat-to-beat R-R intervals were measured for 10 min both before and after combined acupuncture stimulations to CV12, ST25, and CV6. HRV was analyzed for the power of high-frequency (HF) and low-frequency (LF) components, and the LF-to-HF power ratio (LF/HF). After the combined acupuncture stimulations, the heart rate decreased (p = 0.0002) with respect of the pre-stimulation period, HF and LF increased (p = 0.0007 and 0.0005 respectively), while LF/HF did not change significantly. The heart rate decreased and the high-frequency component, which reflects cardiac vagal activity, increased after the acupuncture stimulations, while LF/HF, which reflects sympathetic activity, did not change. Our observations suggest that the combined acupuncture stimulations to the abdomen decrease heart rate through an enhancement of cardiac vagal activity. In this study, HRV analysis allowed us to detect the effects of acupuncture stimulations on cardiac autonomic functions. To elucidate the entire picture of the autonomic effects of acupuncture, it will be necessary to evaluate autonomic neural effects on other organs such as gastrointestinal systems.