Role of extrinsic innervation in modulating nitrergic transmission in the canine ileocolonic region

Somchai Leelakusolvong, Michael G. Sarr, Steven M. Miller, Sidney F. Phillips, Adil E. Bharucha

Research output: Contribution to journalArticlepeer-review

10 Scopus citations


The human colon can dilate, often to life-threatening proportions. Our aim was to explore nitrergic mechanisms underlying colonic dilation in conscious dogs with enterically isolated ileocolonic loops either extrinsically innervated (n = 4) or extrinsically denervated (n = 4). We recorded phasic pressures in ileum and ileocolonic sphincter (ICS), colonic tone, compliance, and relaxation during ileal distension. By NADPH-diaphorase histochemistry, we assessed effects of extrinsic denervation and enteric isolation on nitrergic fibers. Extrinsic denervation increased phasic pressures in ileum, ICS, and colon and abolished ICS and colonic relaxation in response to ileal distension. The nitric oxide synthase (NOS) inhibitor Nω-nitro-L-arginine (L-NNA) increased phasic pressures at all sites and ICS tone but did not abolish colonic relaxation during ileal distension in innervated loops. L-NNA reduced compliance and induced colonic high-amplitude propagated contractions in denervated loops. The NOS substrate donor L-arginine reversed effects of L-NNA. The number of NADPH-diaphorase fibers increased in both enterically isolated preparations. Nonnitrergic extrinsic nerve pathways mediate reflex colonic relaxation during ileal distension. Enteric isolation augments the number of NOS fibers, an effect not modified by extrinsic denervation.

Original languageEnglish (US)
Pages (from-to)G230-G239
JournalAmerican Journal of Physiology - Gastrointestinal and Liver Physiology
Issue number1 46-1
StatePublished - 2002


  • Colonic motility
  • Extrinsic denervation
  • Ileal motility
  • Ileocolonic sphincter
  • Nitrergic nerves
  • Nitric oxide
  • Nitric oxide synthase

ASJC Scopus subject areas

  • Physiology
  • Hepatology
  • Gastroenterology
  • Physiology (medical)


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