PT  - JOURNAL ARTICLE
AU  - T V Nowak
AU  - B Harrington
TI  - Evidence for diminished inhibitory neuromuscular transmission in distal small intestine.
DP  - 1987 Feb 01
TA  - Journal of Pharmacology and Experimental Therapeutics
PG  - 381--387
VI  - 240
IP  - 2
4099  - http://jpet.aspetjournals.org/content/240/2/381.short
4100  - http://jpet.aspetjournals.org/content/240/2/381.full
SO  - J Pharmacol Exp Ther1987 Feb 01; 240
AB  - 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.