Distinct Muscarinic Acetylcholine Receptor Subtypes Contribute to Stability and Growth, But Not Compensatory Plasticity, of Neuromuscular Synapses
Open Access
- 25 November 2009
- journal article
- Published by Society for Neuroscience in Journal of Neuroscience
- Vol. 29 (47), 14942-14955
- https://doi.org/10.1523/jneurosci.2276-09.2009
Abstract
Muscarinic acetylcholine receptors (mAChRs) modulate synaptic function, but whether they influence synaptic structure remains unknown. At neuromuscular junctions (NMJs), mAChRs have been implicated in compensatory sprouting of axon terminals in paralyzed or denervated muscles. Here we used pharmacological and genetic inhibition and localization studies of mAChR subtypes at mouse NMJs to demonstrate their roles in synaptic stability and growth but not in compensatory sprouting. M2 mAChRs were present solely in motor neurons, whereas M1, M3, and M5 mAChRs were associated with Schwann cells and/or muscle fibers. Blockade of all five mAChR subtypes with atropine evoked pronounced effects, including terminal sprouting, terminal withdrawal, and muscle fiber atrophy. In contrast, methoctramine, an M2/4-preferring antagonist, induced terminal sprouting and terminal withdrawal, but no muscle fiber atrophy. Consistent with this observation, M2−/− but no other mAChR mutant mice exhibited spontaneous sprouting accompanied by extensive loss of parental terminal arbors. Terminal sprouting, however, seemed not to be the causative defect because partial loss of terminal branches was common even in the M2−/− NMJs without sprouting. Moreover, compensatory sprouting after paralysis or partial denervation was normal in mice deficient in M2 or other mAChR subtypes. We also found that many NMJs of M5−/− mice were exceptionally small and reduced in proportion to the size of parental muscle fibers. These findings show that axon terminals are unstable without M2 and that muscle fiber growth is defective without M5. Subtype-specific muscarinic signaling provides a novel means for coordinating activity-dependent development and maintenance of the tripartite synapse.Keywords
This publication has 93 references indexed in Scilit:
- Regulation of STARS and its downstream targets suggest a novel pathway involved in human skeletal muscle hypertrophy and atrophyThe Journal of Physiology, 2009
- Impaired Synaptic Vesicle Release and Immaturity of Neuromuscular Junctions in Spinal Muscular Atrophy MiceJournal of Neuroscience, 2009
- Formin-Dependent Synaptic Growth: Evidence That Dlar Signals via Diaphanous to Modulate Synaptic Actin and Dynamic Pioneer MicrotubulesJournal of Neuroscience, 2008
- Lack of Specificity of Commercially Available Antisera: Better Specifications NeededJournal of Histochemistry & Cytochemistry, 2008
- Synthesis, trafficking, and localization of muscarinic acetylcholine receptorsPharmacology & Therapeutics, 2008
- Recovery of mouse neuromuscular junctions from single and repeated injections of botulinum neurotoxin AThe Journal of Physiology, 2008
- Guide to Receptors and Channels (GRAC), 3rd editionBritish Journal of Pharmacology, 2008
- Ciliary neurotrophic factor is not required for terminal sprouting and compensatory reinnervation of neuromuscular synapses: Re-evaluation of CNTF null miceExperimental Neurology, 2007
- Cdc42 GTPase-activating protein deficiency promotes genomic instability and premature aging-like phenotypesProceedings of the National Academy of Sciences of the United States of America, 2007
- Muscarinic receptors: their distribution and function in body systems, and the implications for treating overactive bladderBritish Journal of Pharmacology, 2006