Segmentation induced by intraluminal fatty acid in isolated guinea‐pig duodenum and jejunum

Abstract

Small intestinal movements depend on the composition of the chyme with mixing predominating at high nutrient levels and propulsion being prevalent at low nutrient levels. The mechanisms coupling nutrients to motility are unknown. We used computer analysis of video recordings of isolated guinea-pig duodenum, jejunum and ileum to examine movements induced by a fatty acid, decanoic acid. Increasing intraluminal pressure past a threshold using control saline consistently evoked propulsive reflexes: lumen-occluding constrictions appeared at the oral end propagating at 20.4 ± 2.4 mm s −1 (mean ± S.D., jejunum) to the anal end before being repeated until the intraluminal pressure was returned to control. Subthreshold pressure increases sometimes evoked a transient series of constrictions appearing at the oral end and propagating anally at 18.4 ± 4.7 mm s −1 (jejunum). At basal pressures, decanoic acid dose-dependently induced motor activity consisting of 40-60 s episodes of constrictions separated by 40-200 s periods of quiescence and lasting up to 2 h. Five contraction patterns were identified within episodes including localized stationary constrictions; constrictions that propagated slowly (5-8 mm s −1 ) for short distances orally or anally; and constrictions that propagated orally or anally for the length of the preparation at 14-20 mm s −1 . Decanoic acid induced motor activity was reversibly abolished by tetrodotoxin (3 µM), hyoscine (1 µM) and hexamethonium (100 µM ), but was insensitive to blockade of P2 purinoceptors by PPADS (60 µM). Thus, decanoic acid induces motor activity equivalent to segmentation in guinea-pig small intestine in vitro and this depends on intrinsic neural pathways.

Purinergic mechanisms in the control of gastrointestinal motility

“…Nutrient-induced motor activity also includes circularmuscle constrictions that propagate slowly for short distances orally or anally [139]. Like the stationary contractions, these short-length propagating contractions may be limited by large apamin-sensitive IJPs that are seen just beyond the point at which the contraction disappears [131].…”

“…PPADS does not alter the threshold of propulsive reflex activation by saline distension [35], nor does it change the motor activity induced by luminal nutrients in the guinea-pig small intestine [139]. A reduction in threshold for initiation of propulsion by PPADS that was antagonised by suramin has also been reported [162].…”

Ageing and Gastrointestinal Sensory Function

“…And therefore the attention shifted to the enteric nervous system to fi nd a neural program that would change peristalsis into segmentation. One hypothesis states that cholinergic motor neurons acting on muscarinic receptors periodically activate the musculature and that inhibitory neurons surround this contraction to fi nalize the motor pattern (Gwynne and Bornstein 2007 ;Gwynne et al 2004 ). Another study states that CCK and 5-HT are critical for the generation of segmentation (Ellis et al 2013 ).…”

“…Until I saw a perfect segmentation motor pattern in the presence of TTX . While on sabbatical at the laboratory of Jihong Chen at Wuhan University we experimented with decanoic acid that had been shown to induce segmentation (Gwynne et al 2004 ). We discovered a remarkable feature: decanoic acid changed the electrical activity of the intestine from regular slow waves to a waxing and waning pattern.…”

Spatiotemporal Mapping of Motility in <em>Ex Vivo</em> Preparations of the Intestines

“…Initial approaches, first described for intestinal segments in the late 1990s 7,8 , depended on investigator-designed software to analyze video recording; several groups have now created or modified software for this purpose 2,[8][9][10][11][12] . While many groups have generated their own software packages or plugins, they all analyze diameters of a tissue segment and convert those various diameters to grayscale representation.…”