Nerve terminal sprouting in botulinum type-A treated mouse levator auris longus muscle

Neuromuscul Disord. 1996 May;6(3):177-85. doi: 10.1016/0960-8966(96)00041-7.


The marked outgrowth of the motor nerve terminal arborization triggered by an in vivo local injection of Clostridium botulinum type-A toxin in the mouse levator auris longus muscle was studied with morphological and immunochemical approaches. The increase in total nerve terminal length depended on the time elapsed after toxin administration and was due to both increased number of terminal branches and branch length as revealed by a quantitative morphological analysis of whole mounts using the combined cholinesterase-silver stain. Nerve terminal sprouts increased in number, length and complexity even after the functional recovery of neuromuscular transmission had occurred as revealed by electrophysiological examination. Although we cannot exclude that transmitter release sites from the original nerve terminal arborization may still be functional after botulinum type-A toxin (BoTx-A) treatment, it is likely that newly formed functional release sites on the sprouts play a major role in the functional recovery of neuromuscular transmission. The presence of an immunoreactivity to synaptophysin and synaptotagmin-II, integral proteins of synaptic vesicles, gives support to our previous findings suggesting that nerve terminal sprouts have the molecular machinery for acetylcholine release.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Botulinum Toxins, Type A / pharmacology*
  • Cholinesterases / analysis
  • Electric Stimulation
  • Evoked Potentials / drug effects
  • Female
  • Mice
  • Motor Endplate / drug effects
  • Motor Endplate / physiology
  • Motor Neurons / drug effects
  • Motor Neurons / physiology
  • Muscle, Skeletal / drug effects
  • Muscle, Skeletal / innervation*
  • Nerve Endings / drug effects*
  • Nerve Endings / physiology
  • Nerve Endings / ultrastructure
  • Nerve Tissue Proteins / analysis
  • Neuromuscular Junction / drug effects
  • Neuromuscular Junction / physiology*
  • Neuromuscular Junction / ultrastructure
  • Synaptic Transmission / drug effects*
  • Synaptophysin / analysis
  • Synaptotagmin II


  • Nerve Tissue Proteins
  • Synaptophysin
  • Synaptotagmin II
  • Syt2 protein, mouse
  • Cholinesterases
  • Botulinum Toxins, Type A