Induction of a non-rhythmic motor pattern by nitric oxide in hatchling Rana temporaria embryos

David L. McLean, Jonathan R. McDearmid, Keith T. Sillar*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

10 Scopus citations

Abstract

Nitric oxide (NO) is a ubiquitous neuromodulator with a diverse array of functions in a variety of brain regions, but a role for NO in the generation of locomotor activity has yet to be demonstrated. The possibility that NO is involved in the generation of motor activity in embryos of the frog Rana temporaria was investigated using the NO donors S-nitroso-n-acetylpenicillamine (SNAP; 100-500 μmol l-1) and diethylamine nitric oxide complex sodium (DEANO; 25-100 μmol l-1). Immobilised Rana temporaria embryos generate a non-rhythmic 'lashing' motor pattern either spontaneously or in response to dimming of the experimental bath illumination. Bath-applied NO donors triggered a qualitatively similar motor pattern in which non-rhythmic motor bursts were generated contra- and ipsilaterally down the length of the body. The inactive precursor of SNAP, n-acetyl-penicillamine (NAP), at equivalent concentrations did not trigger motor activity. NO donors failed to initiate swimming and had no measurable effects on the parameters of swimming induced by electrical stimulation. Intracellular recordings with potassium-acetate-filled electrodes revealed that the bursts of ventral root discharge induced by NO donors were accompanied by phasic depolarisations in motor neurons. During the inter-burst intervals, periods of substantial membrane hyperpolarisation below the normal resting potential were observed, presumably coincident with contralateral ventral root activity. With KCl-filled electrodes, inhibitory potentials were strongly depolarising, suggesting that inhibition was Cl--dependent. The synaptic drive seen in motor neurons after dimming of the illumination was very similar to that induced by the NO donors. NADPH-diaphorase histochemistry identified putative endogenous sources of NO in the central nervous system and the skin. Three populations of bilaterally symmetrical neurons were identified within the brainstem. Some of these neurons had contralateral projections and many had axonal processes that projected to and entered the marginal zones of the spinal cord, suggesting that they were reticulospinal.

Original languageEnglish (US)
Pages (from-to)1307-1317
Number of pages11
JournalJournal of Experimental Biology
Volume204
Issue number7
StatePublished - Dec 1 2001

Keywords

  • Frog
  • Histochemistry
  • Motor pattern
  • NADPH diaphorase
  • Nitric oxide
  • Rana temporaria
  • Swimming

ASJC Scopus subject areas

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

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