NADPH diaphorase and nitric oxide synthase colocalization in enteric neurons of canine proximal colon

S. M. Ward, C. Xue, C. W. Shuttleworth, D. S. Bredt, S. H. Snyder, K. M. Sanders

Research output: Contribution to journalArticlepeer-review

162 Scopus citations


Considerable evidence has recently been presented that suggests that nitric oxide (NO) is a nonadrenergic noncholinergic (NANC) neurotransmitter in gastrointestinal tissues. One of the criteria that must be satisfied before this hypothesis can be accepted is that enteric neurons must be shown to contain the enzymatic apparatus necessary to synthesize NO. Specific antibodies have been developed for NO synthase (NOS) isolated from rat cerebellum, and studies have shown that NOS copurifies and colocalizes with NADPH diaphorase activity, a commonly used neural marker. We used antibodies raised against the cerebellar NOS to determine the distribution of NOS-like immunoreactivity (NOS-LI) in enteric neurons of the canine proximal colon. We also tested whether NADPH diaphorase staining would label the population of neurons containing NOS-LI in this species. A subpopulation of neurons in myenteric and submucosal ganglia displayed NOS-LI and were colabeled with NADPH diaphorase. Labeled neurons had morphological characteristics similar to the Dogiel type I morphology. Cryostat sections showed NOS-positive nerve trunks throughout the circular and longitudinal muscle layers, but a high density of NOS-LI was observed within the submucosal pacemaker region, as predicted from physiological studies. These studies provide the first morphological support for the hypothesis that NO serves as a NANC neurotransmitter in the canine colon. The study also shows that the NADPH diaphorase reaction provides a useful method to label cells with NOS-LI.

Original languageEnglish (US)
Pages (from-to)G277-G284
JournalAmerican Journal of Physiology - Gastrointestinal and Liver Physiology
Issue number2 26-2
StatePublished - 1992
Externally publishedYes


  • enteric nervous system
  • gastrointestinal motility
  • nitric oxide synthase
  • nonadrenergic noncholinergic nerves

ASJC Scopus subject areas

  • Physiology
  • Hepatology
  • Gastroenterology
  • Physiology (medical)


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