Journal of Neuroscience, Vol 7, 2019-2024, Copyright © 1987 by Society for Neuroscience
Mechanisms of postsynaptic plasticity: remodeling of the junctional acetylcholine receptor cluster induced by motor nerve terminal outgrowth
WC Yee and A Pestronk
Motor nerve terminal outgrowth (NTO) at neuromuscular junctions (NMJs)
occurs rapidly in response to denervation changes in muscle. We have
previously found that NTO can produce an elongation of the synaptic area of
the NMJ as defined by cholinesterase-silver staining. In the present study,
we examined the effects of NTO on a postsynaptic muscle membrane component,
the usually stable cluster of acetylcholine receptors (AChRs) at the NMJ.
NTO was evoked in rat soleus muscles using botulinum toxin. AChRs were
demonstrated using immunocytochemistry or autoradiography of
alpha-bungarotoxin binding. Our results show that NTO induces rapid
elongation of the cluster of AChRs at the NMJ within 7 d of treatment with
botulinum toxin. The growth in the size of the AChR clusters was
accompanied by an increase in the number of AChRs/NMJ. No elongation of
AChR clusters was seen following surgical denervation, suggesting that
cluster growth is related to NTO and not to denervation changes in muscle
per se. Growth of NMJ-AChR clusters appeared to result primarily from 2
processes: insertion of new AChRs into the NMJ membrane and, surprisingly,
redistribution of preexisting NMJ-AChRs. These results show that NTO can
cause rapid changes in the normally stable cluster of AChRs at the NMJ.
Motor nerve terminals provide a strong and anatomically precise control of
AChRs at the NMJ.