Feline lower esophageal sphincter sling and circular muscles have different functional inhibitory neuronal responses

The lower esophageal sphincter (LES) has a circular muscle component exhibiting spontaneous tone that is relaxed by nitric oxide (NO) and a low-tone sling muscle that contracts vigorously to cholinergic stimulation but with little or no evidence of NO responsiveness. This study dissected the respons...

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Bibliographic Details
Published in:American journal of physiology: Gastrointestinal and liver physiology 2006-01, Vol.53 (1), p.G23
Main Authors: L'Heureux, Marie-Claude, Muinuddin, Ahmad, Gaisano, Herbert Y, Diamant, Nicholas E
Format: Article
Language:English
Subjects:
Muscular system
Neurons
Nitric oxide
Throat
Online Access:Get full text
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Summary:The lower esophageal sphincter (LES) has a circular muscle component exhibiting spontaneous tone that is relaxed by nitric oxide (NO) and a low-tone sling muscle that contracts vigorously to cholinergic stimulation but with little or no evidence of NO responsiveness. This study dissected the responses of the sling muscle to nitrergic innervation in relationship to its cholinergic innervation and circular muscle responses. Motor responses were induced by electrical field stimulation (EFS; 1-30 Hz) of muscle strips from sling and circular regions of the feline LES in the presence of cholinergic receptor inhibition (atropine) or NO synthase inhibition [NG-nitro-L-arginine (L-NNA) plus or minus atropine]. This study showed the following. First, sling muscle developed less intrinsic resting tone compared with circular muscle. Second, with EFS, sling muscle contracted (most at less than or equ al to 10 Hz), whereas circular muscle relaxed >50% by 5 Hz. Third, on neural blockade with atropine or L-NNA plus or minus atropine, 1) sling muscle, although predominantly influenced by excitatory cholinergic stimulation, had a small neural NO-mediated inhibition, with no significant non-NO-mediated inhibition and 2) circular muscle, although little affected by cholinergic influence, underwent relaxation predominantly by neural release of NO and some non-NO inhibitory influence (at higher EFS frequency). Fourth, the sling, precontracted with bethanecol, could relax with NO and some non-NO inhibition. Finally, the tension range of both muscles is similar. In conclusion, sling muscle has limited NO-mediated inhibition to potentially augment or replace sling relaxation effected by switching off its cholinergic excitation. Differences within the LES sling and circular muscles could provide new directions for therapy of LES disorders. [PUBLICATION ABSTRACT]
ISSN:0193-1857
1522-1547