Abstract
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 degrees 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 less than .05) at nearly all parameters of pulse duration, current and frequency. Contraction and relaxation amplitudes were significantly greater in longitudinal than respective circular muscle (P less than .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.
JPET articles become freely available 12 months after publication, and remain freely available for 5 years.Non-open access articles that fall outside this five year window are available only to institutional subscribers and current ASPET members, or through the article purchase feature at the bottom of the page.
|