The main neurotransmitter released at the neuromuscular junction (between a motor neuron and a skeletal muscle fiber) is acetylcholine (ACh).

Quick Scoop

  • At vertebrate neuromuscular junctions, motor neurons store and release acetylcholine from synaptic vesicles into the synaptic cleft when an action potential arrives.
  • Acetylcholine diffuses across the cleft and binds to nicotinic acetylcholine receptors on the muscle end plate, triggering depolarization and ultimately muscle contraction.
  • Because of this role, acetylcholine is described as the primary or principal neurotransmitter at the neuromuscular junction in standard physiology references.

TL;DR: The neurotransmitter released at the neuromuscular junction is acetylcholine.