Large cholinergic nerve terminals on subsets of motoneurons and their relation to muscarinic receptor type 2

J Comp Neurol. 2003 Jun 9;460(4):476-86. doi: 10.1002/cne.10648.


The cholinergic C-bouton is a large nerve terminal found exclusively apposing motoneuron cell somata and proximal dendrites. The origin and function of the C-bouton is not known. An antiserum against the vesicular acetylcholine transporter was used to identify large cholinergic nerve terminals putatively of the C-type in close apposition to motoneuron cell somata. This type of nerve terminal was present in the rat spinal cord ventral horn, but only in some cranial motor nuclei. Fluoro-Gold tracing showed that subsets of spinal motoneuron cell somata were contacted by different numbers of putative C-boutons. Thus, motoneurons innervating an intrinsic foot muscle were contacted by about half the number of cholinergic terminals found on motoneurons of the predominantly fast-twitch gastrocnemius muscle. Slow-twitch soleus motoneurons showed an intermediate innervation. There was a strong correlation between the presence of putative C-boutons and muscarinic receptor 2 (m2)-like immunoreactivity (-LI) within a motor nucleus. By using confocal laser microscopy, the m2-LI appeared to be confined to the motoneuron cell membrane and strongly enriched beneath the C-type nerve terminal. Thus, our results suggested a differential distribution of large cholinergic C-boutons, depending on motoneuron type, and that the presence of this nerve terminal type is associated with m2-LI in the postsynaptic membrane.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Afferent Pathways / chemistry
  • Animals
  • Carrier Proteins / analysis*
  • Cholinergic Fibers / chemistry*
  • Female
  • Fluorescent Antibody Technique
  • Fluorescent Dyes
  • Membrane Transport Proteins*
  • Microscopy, Confocal
  • Motor Neurons / chemistry*
  • Muscle, Skeletal / innervation
  • Presynaptic Terminals / chemistry*
  • Rats
  • Rats, Sprague-Dawley
  • Receptor, Muscarinic M2
  • Receptors, Muscarinic / analysis*
  • Spinal Cord / chemistry*
  • Stilbamidines*
  • Vesicular Acetylcholine Transport Proteins
  • Vesicular Transport Proteins*


  • 2-hydroxy-4,4'-diamidinostilbene, methanesulfonate salt
  • Carrier Proteins
  • Fluorescent Dyes
  • Membrane Transport Proteins
  • Receptor, Muscarinic M2
  • Receptors, Muscarinic
  • Slc18a3 protein, rat
  • Stilbamidines
  • Vesicular Acetylcholine Transport Proteins
  • Vesicular Transport Proteins