APPS November 2002 Meeting Abstract 2418


Charles M.S. Humphreys, Marcello Costa, Simon J.H. Brookes, Department of Physiology and Centre for Neuroscience, Flinders University, GPO Box 2100, Adelaide, South Australia, 5001.

Slow circumferential stretch of the guinea-pig ileum elicits a neurally mediated contraction of rapid onset rate, which corresponds to the initiation of peristalsis1. Myogenic mechanisms have been proposed to play a significant role in intestinal peristalsis in the guinea-pig2. In this study, we compared the mechanisms for the initiation of peristalsis in three regions of the small intestine.

Segments of guinea-pig duodenum, jejunum and ileum, 12mm long, were taken from adult guinea-pigs killed by cervical dislocation and bleeding. Preparations were opened and attached by one edge to a tissue stretcher. The other edge was pinned to the bottom of an organ bath containing Krebs solution maintained at 36oC and bubbled with carbogen. Preparations were stretched at a rate of 100m/s until initiation of peristaltic contraction occurred. When a reproducible contraction was obtained, tetrodotoxin (0.6M) was added to the bath. Parameters measured were: threshold circumferential stretch required to initiate peristalsis, threshold tension, amplitude and area of contractions, and time to peak of contractions.

The threshold stretch required to initiate peristalsis in the ileum was 2.93 0.27 mm above resting circumferential length, compared with 3.17 0.31 mm (duodenum) and 2.90 0.57 mm (jejunum). These values were not significantly different. No significant differences were observed in the amplitudes or areas of contractions. The time to peak of ileal responses was significantly shorter than those in the duodenum and jejunum, and the threshold tension of ileal responses was significantly lower than observed in the duodenum. All contractions were abolished by tetrodotoxin, even by stretching preparations beyond the original threshold by 50%.

These results indicate that similar neurogenic mechanisms are responsible for the initiation of peristalsis in all three regions of the small intestine, with no evidence of myogenic peristalsis.

(1) Brookes SJH, Chen BN, Costa M, Humphreys CMS. Journal of Physiology. 1999;516(2):525-538.

(2) Donnelly G, Jackson TD, Ambrous K, Ye J, Safdar A, Farraway L, Huizinga JD. American Journal of Physiology, Gastrointestinal & Liver Physiology. 2001;280(3):G491-G500.

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