Involvement of brainstem serotonergic interneurons in the development of a vertebrate spinal locomotor circuit

Proc Biol Sci. 1995 Jan 23;259(1354):65-70. doi: 10.1098/rspb.1995.0010.


Brainstem neurons modulate the rhythmic output of spinal locomotor circuitry in adult vertebrates, but how these influences develop is largely unknown. We demonstrate that the ingrowth of serotonergic axons to the spinal cord of Xenopus tadpoles plays a critical role in locomotor burst development by transforming the output of embryonic amphibian swimming circuitry into a more mature and flexible form. Our experiments show that exposure to a monoamine neurotoxin (5,7 dihydroxytryptamine) deletes serotonergic raphespinal projections and prevents the normal maturation of larval swimming. Furthermore, the mature larval rhythm resumes an embryo-like form following either a pharmacological blockade of serotonin receptors or when receptor activation is prevented by acute spinalization.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 5,7-Dihydroxytryptamine / pharmacology
  • Animals
  • Brain Stem / anatomy & histology
  • Brain Stem / physiology*
  • Immunohistochemistry
  • Interneurons / physiology*
  • Larva
  • Locomotion / physiology
  • Neural Pathways
  • Raphe Nuclei / anatomy & histology
  • Raphe Nuclei / physiology
  • Receptors, Serotonin / physiology
  • Serotonin / physiology*
  • Serotonin Antagonists / pharmacology
  • Spinal Cord / anatomy & histology
  • Spinal Cord / physiology*
  • Xenopus laevis / anatomy & histology
  • Xenopus laevis / physiology*


  • Receptors, Serotonin
  • Serotonin Antagonists
  • 5,7-Dihydroxytryptamine
  • Serotonin