Layer-specific thalamocortical innervation in organotypic cultures is prevented by substances that alter neural activity

Eur J Neurosci. 2002 Jul;16(2):345-9. doi: 10.1046/j.1460-9568.2002.02069.x.

Abstract

Cortical layer IV is the major target of thalamocortical axons and many previous studies have shown that the development of this layer-specific innervation can be modelled in vitro by organotypic cocultures of thalamus and cortex. The mechanisms causing thalamic axons to terminate in layer IV are unknown. We used these in vitro models to test the possibility that neural activity plays a part in this termination process by adding substances that raise or lower levels of neural activity to the cocultures. We found that addition of tetrodotoxin or 2-amino-5-phosphonovalerate, to block activity, or potassium, to raise it, all interfered with termination in layer IV. These findings suggest that termination in layer IV requires neural activity at an appropriate level in the thalamocortical system. They also add support to recent findings that show that the importance of neural activity in development may extend to an earlier period than thought previously, to include the correct targeting of axons as well as the later refinement of connections.

MeSH terms

  • 2-Amino-5-phosphonovalerate / pharmacology
  • Action Potentials / drug effects
  • Action Potentials / physiology
  • Animals
  • Animals, Newborn
  • Apoptosis / drug effects
  • Apoptosis / physiology
  • Body Patterning / drug effects
  • Body Patterning / physiology
  • Cell Communication / drug effects
  • Cell Communication / physiology*
  • Cell Differentiation / drug effects
  • Cell Differentiation / physiology*
  • Cell Survival / drug effects
  • Cell Survival / physiology
  • Cerebral Cortex / cytology
  • Cerebral Cortex / embryology*
  • Cerebral Cortex / growth & development
  • Coculture Techniques
  • Fetus
  • Fluorescent Dyes
  • Growth Cones / drug effects
  • Growth Cones / metabolism*
  • Growth Cones / ultrastructure
  • Mice
  • Mice, Inbred BALB C
  • Neural Pathways / cytology
  • Neural Pathways / embryology*
  • Neural Pathways / growth & development
  • Potassium / pharmacology
  • Synaptic Transmission / drug effects
  • Synaptic Transmission / physiology
  • Tetrodotoxin / pharmacology
  • Thalamus / cytology
  • Thalamus / embryology*
  • Thalamus / growth & development

Substances

  • Fluorescent Dyes
  • Tetrodotoxin
  • 2-Amino-5-phosphonovalerate
  • Potassium