Pre- and postsynaptic maturation of the neuromuscular junction during neonatal synapse elimination depends on protein kinase C

J Neurosci Res. 2002 Mar 1;67(5):607-17. doi: 10.1002/jnr.10122.


The distribution of acetylcholine receptors (AChRs) within and around the neuromuscular junction changes dramatically during the first postnatal weeks, a period during which polyneuronal innervation is eliminated. We reported previously that protein kinase C (PKC) activation accelerates postnatal synapse loss. Because of the close relationship between axonal retraction and AChR cluster dispersal, we hypothesize that PKC can modulate morphological maturation changes of the AChR clusters in the postsynaptic membrane during neonatal axonal reduction. We applied substances affecting PKC activity to the neonatal rat levator auris longus muscle in vivo. Muscles were then stained immunohistochemically to detect both AChRs and axons. We found that, during the first postnatal days of normal development, substantial axonal loss preceded the formation of areas in synaptic sites that were free of AChRs, implying that axonal loss could occur independently of changes in AChR cluster organization. Nevertheless, there was a close relationship between axonal loss and AChR organization; PKC modulates both, although differently. Block of PKC activity with calphostin C prevented both AChR loss and axonal loss between postnatal days 4 and 6. PKC may act primarily to influence AChR clusters and not axons, insofar as phorbol ester activation of PKC accelerated changes in receptor aggregates but produced relatively little axon loss.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aging / drug effects
  • Aging / metabolism
  • Animals
  • Animals, Newborn
  • Anterior Horn Cells / cytology
  • Anterior Horn Cells / enzymology
  • Anterior Horn Cells / growth & development*
  • Axons / drug effects
  • Axons / enzymology*
  • Axons / ultrastructure
  • Cell Differentiation / drug effects
  • Cell Differentiation / physiology*
  • Fluorescent Antibody Technique
  • Male
  • Muscle, Skeletal / enzymology
  • Muscle, Skeletal / growth & development*
  • Muscle, Skeletal / innervation
  • Naphthalenes / pharmacology
  • Neuromuscular Junction / cytology
  • Neuromuscular Junction / enzymology
  • Neuromuscular Junction / growth & development*
  • Neuronal Plasticity / drug effects
  • Neuronal Plasticity / physiology*
  • Protein Kinase C / drug effects
  • Protein Kinase C / metabolism*
  • Rats
  • Rats, Sprague-Dawley
  • Receptors, Cholinergic / drug effects
  • Receptors, Cholinergic / metabolism*
  • Synaptic Membranes / drug effects
  • Synaptic Membranes / metabolism
  • Tetradecanoylphorbol Acetate / pharmacology


  • Naphthalenes
  • Receptors, Cholinergic
  • Protein Kinase C
  • calphostin C
  • Tetradecanoylphorbol Acetate