Role of non-neuronal and neuronal acetylcholine in the airways

It is well known that acetylcholine represents a dominant neurotransmitter within mammalian airways and that airway functions, like smooth muscle activity and secretion, are under a continuous cholinergic tone. However, the teleology of this basal cholinergic tone, assumed to originate from neuronal activity, appears difficult to understand, whereas neuronal cholinergic reflex activity can be regarded as a rational regulatory pathway to protect the airways from injury [-]. Based on recent experimental observations, both phenomena may reflect two different biological roles of acetylcholine, acting first as a universal cytomolecule (non-neuronal) and second as a classical neurotransmitter (neuronal).