Activity-dependent editing of neuromuscular synaptic connections.

Work over the past four decades has suggested that neural activity edits synaptic connections throughout the developing nervous system. Synaptic editing is shaped in large part by competitive interactions among different inputs innervating the same target cell that profoundly influence synaptic strength and structure. While competition plays out among presynaptic inputs that anterogradely influence their targets, postsynaptic target cells also modulate competition, in part through retrograde interactions that modulate presynaptic neurotransmitter release. One of the most useful synapses for studying how neural activity mediates synaptic editing is the connections between spinal motor neurons and skeletal muscle fibers, called neuromuscular junctions. Here we review current ideas about the role of activity in editing neuromuscular synaptic connections. The mechanisms by which activity mediates synaptic competition at these peripheral synapses are relevant to understanding how neural circuits in the central nervous system are continually altered by experience throughout life.