These authors contributed equally to this work.
On the mechanism of action of muscle fibre activity in synapse competition and elimination at the mammalian neuromuscular junction
Article first published online: 29 MAY 2009
© The Authors (2009). Journal Compilation © Federation of European Neuroscience Societies and Blackwell Publishing Ltd
European Journal of Neuroscience
Volume 29, Issue 12, pages 2327–2334, June 2009
How to Cite
Favero, M., Massella, O., Cangiano, A. and Buffelli, M. (2009), On the mechanism of action of muscle fibre activity in synapse competition and elimination at the mammalian neuromuscular junction. European Journal of Neuroscience, 29: 2327–2334. doi: 10.1111/j.1460-9568.2009.06779.x
- Issue published online: 15 JUN 2009
- Article first published online: 29 MAY 2009
- motor endplate;
- muscle development;
- polyneuronal innervation;
- synapse elimination
Activity-dependent competition plays a crucial role in the refinement of synaptic connections in the peripheral and central nervous system. The reduction in number of axons innervating each neuromuscular junction during development, i.e. synapse elimination, appears to be one such competitive activity-driven event. Recently, we showed that asynchronous firing of competing presynaptic terminals is a key player in synapse elimination. Although some previous studies suggested that activity of the postsynaptic cell may be an intermediary in the disposal of redundant presynaptic inputs, the mechanism involved remains unknown. In the present study, in order to assess the role of evoked muscle activity in this process, we inhibited the generation of postsynaptic action potentials in muscle fibers in vivo, through the overexpression of inwardly rectifying Kir2.1 and Kir2.2 channels, via electroporation of the soleus muscle in the mouse hindlimb. Electrophysiological and morphological data show that overexpression of potassium channels in the endplate region of neonatal muscle fibres induces membrane hyperpolarization and an increase in conductance, inhibition of the action potential mechanism and prolonged persistence of polyneuronal innervation. These changes are not seen in muscle fibres with overexpression of a non-conducting Kir2.1 mutant. Our results are compatible with the interpretation that the block of action potential generation, even in single endplates, can inhibit synapse elimination through local signalling.