Ng-nitro-L-arginine reduces nonadrenergic, noncholinergic relaxations of human gut

Gastroenterology. 1992 Feb;102(2):679-83. doi: 10.1016/0016-5085(92)90120-n.


The aim of this study was to determine whether nonadrenergic, noncholinergic inhibitory neurotransmission in human circular sigmoid colonic and internal anal sphincter muscle involves release of a nitric oxide-like substance. Colonic and sphincter muscle respond to electrical field stimulation by giving nonadrenergic, noncholinergic relaxations. After-contractions always occur in colonic muscle but only sometimes in sphincter muscle. Ng-Nitro-L-arginine abolished relaxations of sphincter muscle and partially reduced those of colonic muscle. After-contractions were undiminished as were relaxations of sphincter muscle to sodium nitroprusside. The effects of Ng-nitro-L-arginine were reversed by L-arginine. The results suggest that nitric oxide is possibly the neurotransmitter mediating nonadrenergic, noncholinergic relaxations of the human internal anal sphincter muscle.

MeSH terms

  • Anal Canal / drug effects
  • Anal Canal / innervation
  • Anal Canal / physiology*
  • Arginine / analogs & derivatives*
  • Arginine / pharmacology
  • Colon, Sigmoid / drug effects
  • Colon, Sigmoid / innervation
  • Colon, Sigmoid / physiology*
  • Humans
  • In Vitro Techniques
  • Muscle Relaxation / drug effects
  • Muscle, Smooth / drug effects
  • Muscle, Smooth / physiology
  • Nitroarginine


  • Nitroarginine
  • Arginine