Prejunctional nicotinic acetylcholine receptor (Prejunctional nAChR)

The prejunctional nicotinic acetylcholine receptor (nAChR) is a specialized ligand-gated ion channel located on the presynaptic motor nerve terminal at the neuromuscular junction (NMJ). Unlike the postjunctional receptors found on the muscle endplate, these prejunctional receptors are typically composed of neuronal-type subunits, most commonly the alpha-3 and beta-2 (α3β2) or alpha-7 (α7) configurations (Faria et al., 2003, PubMed: 12611930). Their primary physiological role is to mediate a positive feedback mechanism: when acetylcholine is released into the synaptic cleft, it binds to these receptors to trigger the mobilization of additional acetylcholine vesicles from the reserve pool to the readily releasable pool. This ensures that the supply of neurotransmitter is maintained during periods of high-frequency neuronal firing, preventing synaptic fatigue. In clinical anesthesia, non-depolarizing neuromuscular blocking agents (NMBAs) such as rocuronium and vecuronium act as antagonists at these sites. This blockade is clinically identified by the phenomenon of 'fade' during train-of-four (TOF) or tetanic nerve stimulation, where the strength of muscle contraction diminishes with successive stimuli because the nerve cannot replenish acetylcholine fast enough (Jonsson et al., 2006, PubMed: 16478935; StatPearls, 2023, NBK536918).

Other names

Presynaptic nicotinic acetylcholine receptorNeuronal nicotinic receptor at the motor nerve terminalPrejunctional nAChR at the neuromuscular junctionAlpha-3-beta-2 nicotinic receptor (at the NMJ)

Antagonism of prejunctional nicotinic receptors inhibits the positive feedback loop responsible for mobilizing acetylcholine vesicles from the reserve pool to the active zone, leading to a progressive decrease in neurotransmitter release during repetitive stimulation (StatPearls, 2023, NBK536918; PubMed: 16478935).