The distribution of NADPH-diaphorase-labelled interneurons and the role of nitric oxide in the swimming system of Xenopus laevis larvae

David L. McLean, Keith T. Sillar*

*Corresponding author for this work

Research output: Contribution to journalArticle

49 Scopus citations

Abstract

The possible involvement of the free radical gas nitric oxide (NO) in the modulation of spinal rhythm-generating networks has been studied using Xenopus laevis larvae. Using NADPH-diaphorase histochemistry, three putative populations of nitric oxide synthase (NOS)-containing cells were identified in the brainstem. The position and morphology of the largest and most caudal population suggested that a proportion of these neurons is reticulospinal. The possible contribution of nitrergic neurons to the control of swimming activity was examined by manipulating exogenous and endogenous NO concentrations in vivo with an NO donor (SNAP, 100-500 μmol l-1) and NOS inhibitors (L-NAME and L-NNA, 0.5-5 mmol l-1), respectively. In the presence of SNAP, swim episode duration decreased and cycle period increased, whereas the NOS inhibitors had the opposite effects. We conclude from these data that the endogenous release of NO from brainstem neurons extrinsic to the spinal cord of Xenopus laevis larvae exerts a continuous modulatory influence on swimming activity, functioning like a 'brake'. Although the exact level at which NO impinges upon the swimming rhythm generator has yet to be determined, the predominantly inhibitory effect of NO suggests that the underlying mechanisms of NO action could involve modulation of synaptic transmission and/or direct effects on neuronal membrane properties.

Original languageEnglish (US)
Pages (from-to)705-713
Number of pages9
JournalJournal of Experimental Biology
Volume203
Issue number4
StatePublished - Feb 1 2000

Keywords

  • Brainstem neuron
  • Locomotion
  • Modulation
  • NADPH-diaphorase
  • Nitric oxide
  • Swimming
  • Vertebrate
  • Xenopus laevis

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Physiology
  • Aquatic Science
  • Animal Science and Zoology
  • Molecular Biology
  • Insect Science

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