Neuropeptides are, by definition, small amino acid components that are localized to neurons. Originally described in the gastrointestinal tract, neuropeptides were first termed “gut hormones.” Subsequently, the same peptides were also found in the brain and were termed “gut-brain hormones.” It is now apparent, however, that these peptides are present throughout the body and may be produced by, and localized to, cells other than cells of the central and peripheral nervous systems. In the respiratory tract, neuropeptides are located in neurons, neuroendocrine cells, and inflammatory cells. Neuroendocrine cells are granulated epithelial cells distributed throughout the conducting airways that contain several peptides, including calcitonin, katacalcin, CGRP, and bombesin.’ Neuropeptides, such as VIP, have been identified in various inflammatory cells, including eosinophils,2