Origins of motility patterns in isolated arterially perfused rat intestine.

ABSTRACT

BACKGROUND/AIMS: Assessment of the neuromuscular control of small intestinal motility and movement of luminal contents is hampered in vivo by measurement techniques and in vitro by tissue viability. The aim of this study was to establish the structural and functional integrity of an isolated segment of rat ileum and characterize its motility. METHODS: Segments of rat ileum were perfused arterially with oxygenated fluorocarbon and luminally with saline. Oral and aboral pressures were correlated with conformational changes detected by concurrent video imaging. RESULTS: Light and electron microscopy showed no neuromuscular abnormalities after experiments, and acetylcholine-induced pressure amplitudes were unchanged during experiments. Under basal conditions, low-frequency contractions showing constant frequency (0.27/min) and amplitudes (oral, 17 hPa; aboral, 15 hPa) corresponded to luminally occlusive aborally propagated contractions, which were eliminated by tetrodotoxin. High-frequency contractions with a constant frequency (27/min) were also seen; their basal amplitude (0.3 hPa) increased immediately before and after low-frequency contractions and after tetrodotoxin. Tetrodotoxin also increased basal intestinal tone. CONCLUSIONS: An isolated, arterially perfused segment of rat ileum retains structural and functional integrity. It shows low-frequency propulsive contractions, controlled by the enteric nervous system, and myogenic high-frequency contractions, probably subject to tonic neural inhibition.