The influence of myenteric nerves on duodenal muscle contraction and relaxation was examined in vitro and compared with muscle responses from the ileum. Proximal and distal rat small intestine was cut into strips measuring 6.0 X 10.0 mm. Strips cut along the oral-caudal axis were called longitudinal strips, whereas those cut 90° to that axis were called circular strips. The strips were stretched to their optimal lengths and subjected to electrical field stimulation (0.1-1.0 msec pulse duration, 30-300 mA, 2-26 Hz) in the presence of Krebs' solution and Krebs' plus atropine, 10-6 M. Field stimulation produced contraction responses that were inhibited by atropine and relaxation responses that were augmented by atropine. Muscarinic blockade abolished completely contraction in circular muscle, but atropine-resistant contractions persisted in the longitudinal strips. Proximal muscle showed significantly greater relaxation responses compared to distal muscle (P < .05) at nearly all parameters of pulse duration, current and frequency. Contraction and relaxation amplitudes were significantly greater in longitudinal than in respective circular muscle (P < .05) at either site in the intestine. Thus, not only do the two muscle layers differ in their respective nerve supplies, but inhibitory neuromuscular transmission appears to have a greater influence in proximal than distal intestine.
|Original language||English (US)|
|Number of pages||7|
|Journal||Journal of Pharmacology and Experimental Therapeutics|
|State||Published - 1987|
ASJC Scopus subject areas
- Molecular Medicine