Effects of acupuncture at Sibai (ST 2) acupoint on neuronal discharge in rat nucleus tractus solitarius

BACKGROUND: Electrophysiology can prove the integration of afferent information from the stomach meridian of Foot-Yangming in the nucleus tractus solitarius (NTS) and objectively describe the specific association between meridian vessels and Zang Fu organs. OBJECTIVE: To investigate the effects of afferent information from acupuncture at Sibai (ST 2) acupoint on neuronal discharge in rat NTS. DESIGN, TIME AND SETTING: A randomized, controlled, animal experiment was performed at the Key Laboratory of Meridian-Vessels and Zang Fu Organs, Traditional Chinese Medicine University of Hunan, State Administration of Traditional Chinese Medicine, and Key Laboratory of Acupuncture, Moxibustion, and the Biological Information of Hunan Higher Education Institutes, between December 2005 and October 2008. MATERIALS: A total of 52 Sprague Dawley rats, of either gender, aged 4 months, were included in this study. Acupuncture needles of 0.32 mm (diameter) x 40 mm (length) were used. METHODS: An extracellular recording protocol was applied. The Sibai (ST 2) acupoint in the stomach meridian of Foot-Yangming was used as an acupuncture point (acupoint). Simultaneously, Dicang (ST 4) and Neiting (ST 44) acupoints in the stomach meridian of Foot-Yangming, Quanliao (SI 18) acupoint in the small intestine meridian of Hand-Taiyang, and a non-acupoint lateral to Sibai (ST 2) acupoint, were selected as controls. The Sibai (ST 2) acupoint was stimulated for 30 seconds, by hand acupuncture through twirling and rotating, to determine the neurons responding to body surface stimulation in the NTS. MAIN OUTCOME MEASURES: Frequency of responding NTS neurons after acupuncture at four acupoints including Sibai (ST 2), Dicang (ST 4), Neiting (ST 44) and Quanliao (SI 18) and one non-acupoint. RESULTS: The frequency of responding NTS neurons was significantly higher after acupuncture at Sibai than at control sites including the Dicang (ST 4), Neiting (ST 44) and Quanliao (SI 18) acupoints and at the non-acupoint (P < 0.01). The frequency of responding NTS neurons at Dicang (ST 4) and Quanliao (SI 18) was significantly higher than at Quanliao (SI 18) and the non-acupoint (P < 0.05). The rate of frequency change of responding NTS neurons for the Sibai (ST 2), Dicang (ST 4), Neiting (ST 44), and Quanliao (SI 18) acupoints as well as the non-acupoint was (35.08 +/- 4.80) %, (28.25 +/- 5.46) %, (27.57 +/- 4.87) %, (20.02 +/- 4.23) %, and (18.55 +/- 2.49) % respectively. Simultaneously, significant differences existed between Sibai (ST 2) and the other acupoints (P < 0.05 or P < 0.01). CONCLUSION: Compared with the Dicang (ST 4) and Neiting (ST 44) acupoints in the stomach meridian of Foot-Yangming, Quanliao (SI 18) acupoint in the small intestine meridian of Hand-Taiyang, and the non-acupoint lateral to Sibai (ST 2) acupoint, the Sibai (ST 2) acupoint in the stomach meridian of Foot-Yangming is more closely related to the NTS. In the stomach meridian of Foot-Yangming, afferent information is different in distant and near Shu acupoints, indicating that each Shu acupoint has its own specificity.