Journal of Neuroscience, Vol 5, 751-758, Copyright © 1985 by Society for Neuroscience
Motor nerve terminal outgrowth and acetylcholine receptors: inhibition of terminal outgrowth by alpha-bungarotoxin and anti-acetylcholine receptor antibody
A Pestronk and DB Drachman
Motor nerves undergo extensive terminal outgrowth when the muscles they
supply are "functionally denervated." In this study, we have investigated
the role of the acetylcholine receptors (AChRs), newly appearing in such
muscles, in promoting nerve terminal outgrowth. The amount of outgrowth was
determined by morphometric measurement of nerve terminal branching,
endplate length, and ultraterminal sprouts, in
cholinesterase-silver-stained neuromuscular junctions. Presynaptic
neuromuscular blockade with botulinum toxin induced pronounced nerve
terminal outgrowth in both the rat and mouse soleus muscles, although
ultraterminal sprouts did not occur in the rat soleus. By contrast,
postsynaptic neuromuscular blockade with alpha-bungarotoxin (alpha- BuTx)
induced little or no terminal outgrowth, although it caused "functional
denervation." Moreover, alpha-BuTx and anti-AChR antibody inhibited the
terminal outgrowth otherwise induced by botulinum toxin. Other types of
motor nerve growth, such as nerve regeneration, were unaffected by these
agents. Our results are consistent with the concept that extrajunctional
AChRs in skeletal muscle play an important role in the control of motor
nerve terminal outgrowth at neuromuscular junctions.