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

Coordinated contractions across the small and large intestines via the ileocecal junction (ICJ) are critical to healthy gastrointestinal function and are in part governed by myoelectrical activity. In this study, the spatiotemporal characteristics of the bioelectrical 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 ce-cum 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. Bioelectrical activity was recorded within the ICJ and AC, revealing complex interactions of slow waves, spike bursts, and bioelectrical quiescence. This suggests the involvement of myogenic coordination when regulating motility between the small and large intestines. Mean slow wave frequency between regions did not vary signifi- cantly (13.74-17.16 cycles/min). Slow waves in the SR propagated with significantly faster speeds (18.51 +/- 1.57 mm/s) compared with 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 with 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. NEW & NOTEWORTHY Competing slow wave pacemakers were observed in the terminal ileum and sacculus rotundus. Prevalent oral propagation in the sacculus rotundus toward the terminal ileum potentially acts as a brake mechanism limiting out-flow. Slow waves and periods of quiescence at the ileocecal junction suggest that activation may depend on the coregulatory flow and distention pathways. Slow waves and spike bursts in the cecum impart a role in the coordination of motility.interstitial cell of Cajal; myoelectrical activity; slow wave; spike bursts

Automated summary

Coordinated contractions across the ICJ are crucial for healthy gastrointestinal function, and their regulation is partly dependent on myoelectrical activity. This study quantified the spatiotemporal characteristics of bioelectrical conduction across the ICJ and adjacent regions in anesthetized rabbits. The findings suggest that bidirectional propagation of slow waves plays a role in coordinating motility between the small and large intestines.