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The nucleus of the solitary tract (nucleus tractus solitarii; NTS) is a primary center for both visceral afferents and somatic afferents. Previous experiments have demonstrated that the NTS is closely connected to the stomach and acupoints in the Yangming Stomach Meridian of Foot (ST Meridian). In this study, extracellular recording and immunochemistry methods were used to analyze the discharge of neurons and c-Fos protein expression in the NTS following acupuncture at different acupoints and a nonacupoint. A total of 104 discharging neurons were detected in the NTS of 52 rats, of which 86 provided complete data. After acupuncture at Sibai (ST 2), Zusanli (ST 36), Neiting (ST 44), Quanliao (SI 18), and the nonacupoint, the neuron response rate in the NTS was 65.12%, 51.16%, 46.51%, 34.88% and 31.40% respectively. For neuron response rate, there was a significant difference among Sibai (ST 2), Zusanli (ST 36), Neiting (ST 44), Quanliao (SI 18), and the nonacupoint (p0.01 or p0.05). In the other 48 rats, the number of c-Fos immunoreactive neurons in the NTS by electroacupuncture (EA) at Sibai (ST 2) group was significantly higher than that EA at other acupoints and the nonacupoint (p0.05 or p0.01). EA at both Zusanli (ST 36) and Neiting (ST 44) increased c-Fos immunoreactive neurons significantly over EA at Quanliao (SI 18) and the nonacupoint (p0.05 or p0.01), while there was no difference between EA at Quanliao (SI 18) and the nonacupoint group (p0.05). The experiments demonstrated that the afferent convergence in NTS are different by body surface points stimulus, which suggests that the NTS might be a primary center in the central nervous system receiving acupoints stimulus from the ST Meridian.

The effect of acupuncture at the acupoints of 12 meridians on gastrointestinal and cardiac electricity in healthy adults was studied. Specific regulation between meridian points and viscera was also investigated. An electrogastrogram (EGG), electrointestinogram (EIG), carotid pulse graph, phonocardiogram and electrocardiogram were obtained in 30 healthy adults before and after acupuncture at various acupoints of 12 meridians. The effects of acupuncture on the amplitude and frequency of the EGG, EIG, pre-ejection period and the left ventricular ejection time were then analyzed. Acupuncture revealed that LR3 decreased the amplitude of the EGG while LI11 (Quchi), SJ5 (Waiguan), ST36 (Zusanli), SP9 (Yinlingquan) and SI6 (Yanglao) increased the amplitude. Multiple comparisons among the latter five acupoints indicated that there were significant differences between SP9, LI11, SJ5 and ST36 (p < 0.01, p < 0.01, p < 0.05) and SI6, LI11 and SJ5 (p < 0.01, p < 0.05). SP9 effected EGG amplitude the most, followed by SI6, ST36, SJ5 and LI11. Four acupoints increased the amplitude of the EIG (p < 0.05), including HT5 (Tongli), GB34 (Yanglingquan), SP9 and SI6. No significant differences were observed between these acupoints, but SI6 showed the most obvious effect on EIG amplitude, followed by GB34, SP9 and HT5. No significant effects on the frequency of the gastrointestinal slow wave or on cardiac function indexes were observed. Effects were observed, however, on pre-ejection period and left ventricular ejection time. Routine acupuncture had no detrimental effects on the stomach, intestine and heart in healthy adults, but instead regulated physiological function within a normal range. These findings demonstrate the existence of specific connections between the meridian points and the viscera. The results suggest that multiple meridians control the same viscus, and the same meridian can regulate the functions of multiple viscera.