Sensory and biomechanical responses to ramp-controlled distension of the human duodenum

Abstract

gersen. Sensory and biomechanical responses to ramp-controlled distension of the human duodenum. Am J Physiol Gastrointest Liver Physiol 284: G461-G471, 2003. First published November 13, 2002 10.1152/ajpgi.00456.2001.-The aim of this study was to develop a new method for investigation of the relationship among the mechanical stimulus, the biomechanical properties, and the visceral perception evoked by volume/ramp-controlled distension in the human duodenum in vivo. An impedance planimetric probe for balloon distension was placed in the third part of the duodenum in seven healthy volunteers. Distension of the duodenum was done at infusion rates of 10, 25, and 50 ml/min. The pump was reversed when level 7 was reached on a visual analog scale ranging from 0 to 10. Distensions were done with and without the administration of the antimuscarinic drug butylscopolamine. The total circumferential tension (T total) and the passive circumferential tension (Tpassive) were determined from the distension tests without and with the administration of butylscopolamine, respectively. T total and Tpassive showed an exponential behavior as a function of strain (a measure of deformation). The active circumferential tension (T active) was computed as TtotalϪTpassive and showed a bellshaped behavior as a function of strain. At low distension intensities, the intensity of sensation at 10 ml/min was significantly higher than that obtained at 25 and 50 ml/min. The coefficient of variation at the pain threshold for circumferential strain (average 4.34) was closer to zero compared with those for volume (8.72), pressure (31.22), and circumferential tension (31.55). This suggests that the mechanoreceptors in the gastrointestinal wall depend primarily on circumferential strain. The stimulus-response functions provided evidence for the existence of low-and high-threshold mechanoreceptors in the human duodenum. Furthermore, the data suggest that high-threshold receptors are nonadapting.cross-sectional area; distensibility; duodenum; pain; lengthtension relationship VISCERAL PAIN IS ONE OF THE most frequent reasons patients seek medical attention. It is well known that distension of the gastrointestinal tract elicits reflexmediated inhibition and stimulation of motility via intrinsic or extrinsic neural circuits and induces visceral perception, such as pain. Previous studies (17,18,37) demonstrate that mechanoreceptors located in the intestinal wall play an important role in the sensory stimulus-response function. From animal studies, it seems evident that some receptors have a high threshold to mechanical stimuli and an encoding function that is evoked by stimuli within the noxious range. Other receptors have a low threshold to mechanical stimuli and an encoding function that spans the range of stimulation intensity from innocuous to noxious (3). Furthermore, some evidence obtained in animal studies indicates that the mucosal nerve endings act as rapidly adapting mechanoreceptors, whereas the intramuscular endings act as slowly adapting mechan...

Mechanosensory properties in the human gastric antrum evaluated using B-mode ultrasonography during volume-controlled antral distension

“…Because changes in the circumference is a proxy of antral deformation, this points to circumferential strain being important for symptom generation. This is consistent with our findings in the esophagus, small intestine, and rectum (1,11,27) and with other studies demonstrating that energy intake and appetite are related to antral area (28).…”

“…The electronic data were amplified, digitized, and stored on the computer for later analysis. A scale for both nonpainful and painful sensations was used as described in previous studies in the upper gut (6,11,26). The intensities of the nonpainful sensations were scored with the following descriptors added to facilitate the scoring: 1 ϭ vague perception of mild sensation, 2 ϭ definite perception of mild sensation, 3 ϭ vague perception of moderate sensation, 4 ϭ definite perception of moderate perception, and 5 ϭ the pain threshold.…”

A Mechanical Model for CCK-Induced Acalculous Gallbladder Pain

“…For the human duodenum in an active state, the strain threshold for pain in the circumferential direction is found to be 1.1 ± 0.2. 15 Similar observations were seen in the human gastrointestinal pain. 11 It is likely that the pain receptors in the nerves respond to the muscle strain.…”

“…1 Applying (15) to the 51 samples, we found that most of these values are much smaller than the threshold of 1.1 ± 0.2 found for human duodenum. 15 Even if we increase the pain threshold to, say [e] = 0.55, the success rate is still only 0.569. This suggests that the mean strains are not useful indicators for the gallbladder pain, and highlights the importance of the spatial distribution.…”

“…It has been shown experimentally that the circumferential strain is responsible for the pain in human oesophagus, 2 duodenum 15 and rectum. 39 It is believed that the mechanoreceptors in the wall of those organs are the (circumferential) strain rather than the total or passive tension.…”