Involvement of nitric oxide in the inhibitory innervation of the human isolated colon

Gastroenterology. 1993 Mar;104(3):690-7. doi: 10.1016/0016-5085(93)91003-z.


Background: The exact nature of the inhibitory nonadrenergic noncholinergic (NANC) neurotransmitter in the human colon is still unknown.

Methods: The present study was designed to investigate the role of nitric oxide (NO) and adenosine 5'-triphosphate (ATP) in circular muscle strips of the human isolated colon.

Results: NO and ATP induced tetrodoloxin-resistant relaxations that mimicked those evoked by nerve stimulation. Apamin inhibited the response to ATP, had a variable effect on the relaxations to transmural stimulation, and had no effect on those to NO or nitroglycerin. NG-nitro-L-arginine (L-NNA) concentration dependently reduced the NANC nerve-mediated relaxations, but had no effect on those to ATP, NO, or nitroglycerin; the L-NNA resistant part of the NANC relaxation to nerve stimulation was further reduced by apamin. The inhibitory effect of L-NNA or the combination of L-NNA and apamin was prevented by L-arginine but not by D-arginine.

Conclusions: These results suggest that NO and another substance, perhaps ATP, are involved in the inhibitory NANC neurotransmission in the circular muscle of the human colon.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Triphosphate / pharmacology
  • Adult
  • Aged
  • Aged, 80 and over
  • Apamin / pharmacology
  • Arginine / analogs & derivatives
  • Arginine / pharmacology
  • Autonomic Nervous System / drug effects*
  • Autonomic Nervous System / physiology
  • Colon / drug effects
  • Colon / innervation*
  • Colon / physiology
  • Humans
  • In Vitro Techniques
  • Middle Aged
  • Muscle Contraction / drug effects
  • Neural Inhibition*
  • Neurotransmitter Agents / pharmacology
  • Nitric Oxide / metabolism
  • Nitric Oxide / pharmacology*
  • Nitroarginine
  • Nitroglycerin / pharmacology
  • Synaptic Transmission
  • Tetrodotoxin / pharmacology


  • Neurotransmitter Agents
  • Nitroarginine
  • Apamin
  • Nitric Oxide
  • Tetrodotoxin
  • Adenosine Triphosphate
  • Arginine
  • Nitroglycerin