An experimental study in guinea pigs examined the functional role of substance P (SP) and its possible interaction with calcitonin gene-related peptide (CGRP) in airway inflammation. Guinea pigs were exposed to ozone (2 ppm for 25 min/day for 2 days) to induce airway inflammation and SP, SP receptor (neurokinin-1 or NK-1R) and CGRP expression were measured during the onset and progression of the inflammation. SP concentrations in lung homogenate and the number of SP immunoreactive cell bodies increased significantly within 24 h, peaked on day 2 and subsequently declined. This was mirrored by CGRP expression implying a strong interactive link between the two neuropeptides. NK-1R expression was induced by CGRP incubation ...