Neuropeptides and asthma.

Although asthma is considered to be an inflammatory disease of the airways, neural mechanisms remain very important. Neural control of airways is far more complex than has been previously recognized. In addition to the classic neural pathways, the nonadrenergic, noncholinergic pathway has been described in the airways of animals and humans. Neuropeptides are present in sensory, parasympathetic, and sympathetic neurons in airways, and have been shown to have proinflammatory effects, such as increased mucus production, microvascular leakage, and smooth muscle contraction. Neuropeptides released from sensory nerves (eg, neurokinin A and substance P) mediate excitatory nonadrenergic, noncholinergic transmission, which causes bronchoconstriction and, possibly, bronchial hyperresponsiveness. Better understanding of neural mechanisms might provide a useful therapeutic approach in the future.