The Influence of Stomach Back-Shu and Front-Mu Points on Insular Functional Connectivity in Functional Dyspepsia Rat Models

Abstract

Functional Dyspepsia (FD) is a common functional gastrointestinal disease, which can reduce the quality of life in patients. Prior research has indicated that insula is closely related to FD and that acupuncture can regulate the functional connectivity (FC) of FD. Therefore, we hypothesized that acupuncture on FD was effected through the insular pathway. To test our hypothesis, we performed electroacupuncture (EA) on FD rat models and then examined the FC between insula and other brain regions through resting-state functional magnetic resonance imaging (rs-fMRI). Seven-day-old male infant Sprague-Dawley (SD) rats were randomly divided into control group, FD model group, and FD acupuncture group, with twelve rats per group (n = 36). Upon establishing successful models, the FD acupuncture group was subjected to EA intervention using Stomach back-shu (BL-21) and front-mu (RN-12) points for ten consecutive days for durations of 20 minutes each day. After intervention, each group was subject to rs-fMRI. The digital image data obtained were analyzed using FC analysis methods. Subsequently, gastric ligation was performed to measure gastric emptying rates. Before EA intervention, the FD model group exhibited decreased functional connections between the insula and a number of brain regions. After EA intervention, FD acupuncture group exhibited increasing FC between insula and regions when compared to the FD model group, such as the primary somatosensory cortex (S1), hippocampal CA3 (CA3), polymorphic layer of dentate gyrus (PoDG), caudate putamen (CPu), and oral pontine reticular nuclei (PnO) (P < 0.05); decreasing FC was also exhibited between insula and regions such as the bilateral primary and secondary motor cortexes (M1/2), paraventricular hypothalamic nucleus (PVA), and limbic cortex (LC). These findings indicate that the effective treatment of FD using EA may be through regulating the abnormal FC between insula and several brain regions, in particular CA3, PoDG, and PVA.

Figure 1

Experimental procedure.

Figure 2

The locations of RN-12 and BL-21 acupuncture points on our rat model.

Figure 3

Example of T2 structural phases.

Figure 4

Scoring of general observations in different groups; data are presented as mean ± SD (n = 6). Note: ^▲P < 0.05, versus control group; ^#P < 0.05, versus FD model group.

Figure 5

Increases in rat body weight in different groups. (a) During phase-one oral gavage administration; (b) during phase-two tail clamping; (c) during EA intervention. Data are presented as mean ± SD (n = 6). Note: ^▲P < 0.05, versus control group.

Figure 6

(a) Comparison of changes in food intake before and after EA intervention; (b) comparison of changes in water intake before and after EA intervention. Data are presented as mean ± SD (n = 6). Note: ^▲P < 0.05, versus control group; ^#P < 0.05, versus FD model group.

Figure 7

Comparison of gastric emptying rates between groups (n = 6). Note: ^▲P < 0.05, versus control group; ^#P < 0.05, versus FD model group.

Figure 8

Regions exhibiting significant functional connections with the insula, FD model group after EA intervention.

Figure 9

Regions exhibiting significant functional connections with the insula, FD model group after EA intervention.