Complementary distribution of NADPH-diaphorase and l-arginine in the snail nervous system

Cell Tissue Res. 2002 Mar;307(3):393-400. doi: 10.1007/s00441-001-0493-8. Epub 2002 Feb 19.

Abstract

Since the interneuronal messenger nitric oxide (NO) can not be stored in neurones, the regulation of the NO-producing enzyme nitric oxide synthase (NOS) is crucial. Neuronal NOS metabolises L-arginine to nitric oxide (NO) and L-citrulline in a Ca(2+)-dependent manner. Thus, availability of L-arginine to NOS may modulate NO production. In this study, we examined the cellular distribution of reduced nicotinamide adenine dinucleotide phosphate (NADPH)-diaphorase, L-arginine and L-citrulline. Using NADPH-diaphorase histochemistry to visualise putative NO-producing cells and immunocytochemistry to localise L-arginine, we showed that the distribution of L-arginine-immunoreactive neurones correlates well with those of NADPH-diaphorase-positive neurones in cerebral ganglia of the pulmonate Helix pomatia. However, substrate and enzyme were visualised in separate but adjacent neurones. We further examined whether NADPH-diaphorase-labelled cells contain the L-citrulline. Following elevation of intracellular Ca(2+) by the Ca(2+) ionophore, ionomycin, or by a high-K(+) solution, the number of L-citrulline-immunoreactive neurones in mesocerebrum and pedal lobe increased up to tenfold. Preincubation of ganglia with the NOS inhibitor N(G)-nitro-L-arginine prevented ionomycin or high-K(+) solution-induced L-citrulline synthesis. Most L-citrulline-immunoreactive neurones contain NADPH-diaphorase activity. In conclusion, these experiments indicate a complementary distribution of NOS and L-arginine and suggest an unknown signalling pathway between neurones to maintain L-arginine and NO homeostasis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Arginine / metabolism*
  • Calcium / metabolism
  • Citrulline / metabolism
  • Ganglia, Invertebrate / cytology
  • Ganglia, Invertebrate / metabolism
  • Helix, Snails / anatomy & histology
  • Helix, Snails / metabolism*
  • Homeostasis
  • NADPH Dehydrogenase / metabolism*
  • Neurons / cytology
  • Neurons / metabolism
  • Nitric Oxide / metabolism
  • Nitric Oxide Synthase / metabolism*

Substances

  • Citrulline
  • Nitric Oxide
  • Arginine
  • Nitric Oxide Synthase
  • NADPH Dehydrogenase
  • Calcium