The bio-electrical conduction system around the ileocecal junction defined through in‑vivo high-resolution mapping in rabbits

Coordinated contractions across the small and large intestine via the ileocecal junction (ICJ) are critical to healthy gastrointestinal function, and are in part governed by myoelectrical activity. In this study, the spatio-temporal characteristics of the bio-electrical conduction across the ICJ and its adjacent regions were quantified in anesthetized rabbits. High-resolution mapping was applied from the terminal ileum (TI) to the sacculus rotundus (SR), across the ICJ and into the beginning of the large intestine at the caecum ampulla coli (AC). Orally propagating slow wave patterns in the SR did not entrain the TI. However, aborally propagating patterns from the TI were able to entrain the SR. Bio-electrical activity was recorded within the ICJ and AC, revealing complex interactions of slow waves, spike bursts and bio-electrical quiescence. This suggests involvement of myogenic coordination when regulating motility between the small and large intestine. Mean slow wave frequency between regions did not vary significantly (13.74-17.16 cpm). Slow waves in the SR propagated with significantly faster speeds (18.51±1.57 mm/s) compared to the TI (14.05±2.53 mm/s, P = 0.0113) and AC (9.56±1.56 mm/s, P = 0.0001). Significantly higher amplitudes were observed in both the TI (0.28±0.13 mV, P = 0.0167) and SR (0.24±0.08 mV, P = 0.0159) within the small intestine compared to the large intestine AC (0.03±0.01 mV). We hypothesize that orally propagating slow waves facilitate a motor-brake pattern in the SR to limit outflow into the ICJ, similar to those previously observed in other gastrointestinal regions.

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