Intraluminal Pressure, Multi‐Dimensional Field Imaging and Fluid Volume Recordings as a Useful Tool to Determine Peristaltic Propulsion

Abstract

IntroductionPeristalsis is a collective process of intestinal muscle contractions for the passage of food through the gastrointestinal tract. Although, peristalsis has been extensively studied using spatiotemporal mapping and pressure transducers both in vivo and in vitro, the quantitative analysis of peristaltic propulsion is not fully understood. Lack of a definitive tool therefore, limited drug discovery in the field of constipation including IBSC. In this study, we used directional lighting, advanced field‐imaging techniques together with intraluminal pressure recordings to determine intestinal diameter, frequency of longitudinal muscle activity and pressure changes as well as velocity of anterograde and retrograde contractions and volume output measurements to help determine the net peristaltic activity.MethodsThe basal activity of intestinal peristalsis in terms of intraluminal pressure (ILP) changes, real‐time changes in longitudinal muscle activity and intestinal lumen diameter were measured in approximately 5 cm long segments from jejunum of mouse small intestine (male, NIH Swiss) in physiological Ringer solution. Intraluminal pressure was recorded using pressure transducers connected to the oral and aboral end of each segment mounted in Perfusion Bath for Tubular Organs, (Harvard apparatus, USA). Longitudinal muscle activity was studied using CVX400 series vision system, and LumiTrax™multi‐spectrum light (Keyence, USA) using multiple tracking points in each intestinal segment. The number, strength, and amplitude of oscillations in terms of intraluminal pressure changes and longitudinal muscle activity was analyzed using custom written programs. Luminal volume output was measured using a photo‐electric drop counter unit.ResultsThe number, amplitude, duration, and frequency of high and low amplitude changes in ILP and longitudinal muscle activity was determined using a lab‐written program. The frequency of longitudinal muscle activity correlated well with the frequency of low and high amplitude pressure changes. Frequency of both these oscillations were found to be 0.7 Hz. A reduction in the ILP was found to induce high amplitude contractions which subsided as the ILP increased. Changes in intestinal diameter with time correlated to ILP changes. A reduction in luminal diameter caused an increase in ILP and when not fully compensated caused increased fluid output. The mean velocity of the contractions over time in the regions tracked was determined to be 2.5 – 2.7mm/sec with peak anterograde contraction velocity of ‐4.06 mm/sec and retrograde contractions of 12 mm/sec. This mean velocity in presence of physiological Ringer solution was thought to determine the direction of contractions along the length of the GI tract under normal conditions.InferenceFrequency of longitudinal muscle activity and ILP oscillation showed similar frequency suggesting common pacemaker activity. The velocity of the contraction and volume output over time will help determine the overall peristaltic movement and could be used as a helpful index to gauge constipation.