Chronic Sacral Nerve Stimulation Inhibits Visceral Hypersensitivity in Diarrhea-Predominant Irritable Bowel Syndrome Rats Model.

OBJECTIVE: Sacral nerve stimulation (SNS) is emerging as a novel treatment for irritable bowel syndrome (IBS). However, its effects are limited, and the underlying mechanisms remain largely unknown. MATERIALS AND METHODS: In this study, rats were divided into three groups (n = 12 rats per group): 1) the SNS group; 2) the sham SNS group (the sham group for short); and 3) the control group. The SNS and sham groups were exposed to chronic and acute stress to establish an IBS model. Electrode implantation surgery was performed in rats with the IBS model. The SNS group received electrical stimulation for 30 minutes every day for seven days. Abdominal withdrawal reflex (AWR) was used to evaluate the effect of SNS on visceral sensitivity in diarrhea-predominant IBS (IBS-D) rats. The frequency domain of heart rate variability (HRV) was analyzed to assess the effect of SNS on regulating the autonomic function. The expression of transient receptor potential vanilloid 1 (TRPV1) in the colon, spinal cord, and hippocampus was detected by immunohistochemistry to explore the mechanism of SNS in IBS-D rats. RESULTS: Compared with the sham group, AWR scores were significantly decreased under different gas volumes of stimulation of 0.4, 0.6, and 0.8 ml for rectal distention in the SNS group (all p < 0.05). However, there was no significant difference <1.0 ml between the two groups (p > 0.05). Compared with the sham group, the frequency domain indexes of HRV were significantly altered. Normalized low-frequency power and low frequency-to-high frequency ratio were significantly decreased, and normalized high-frequency power was significantly increased in the SNS group (all p < 0.05). Moreover, the expression of TRPV1 in the spinal cord and colon in the SNS group was significantly decreased compared with the sham group (both p < 0.05). These results suggested that chronic SNS not only improved the visceral sensitivity and autonomic dysfunction but also decreased the expression of TRPV1 in the spinal cord-gut tissue in IBS-D rats. CONCLUSION: Chronic SNS was found to have an inhibitory effect on visceral hypersensitivity in IBS-D rats, providing experimental evidence for its potential clinical application in IBS.

Vibration of a liquid-filled capillary tube.

Liquid-filled capillary tubes are common structures in nature and engineering fields, which often function via vibration. Although liquid-solid interfacial tension plays important roles in the vibration behavior of the liquid-filled capillary tube, it remains elusive how the interfacial tension influences the natural frequency of capillary tube vibration. To address this, we developed a theory of beam-string structure to analyze the influence of liquid-solid interfacial tension on the vibration of a liquid-filled capillary cantilever. We used glass capillary tubes as a demo and experimentally validated the theory, where the reduced liquid-solid interfacial tension in a capillary tube decreases the natural frequencies of small-order modes. We then performed theoretical analysis and found that the change of elastocapillarity number, slenderness ratio and inner/outer radius ratio of capillary tubes enables: in higher order modes, a nonmonotonic change of natural frequency due to mode transformation between a beam and string; for lower order modes, decrease in the natural frequency to zero (increase from zero) due to mode disappearance (appearance). The developed theory would provide guidelines for high-accuracy design of capillary sensors.