Neuropeptides secreted by sensory afferent nerves in airways may modulate growth of airway epithelial cells. To determine whether airway sensory C-fiber nerves secrete neuropeptides that stimulate airway epithelial cell proliferation, we measured S-phase traversal in guinea pig tracheal epithelial (GPTE) cells after coculture with rat dorsal root ganglion (DRG) cells. GPTE cells were grown in subconfluent culture on collagen-coated filters for 2 days. DRG cells were harvested from newborn rat pups and grown in primary culture for 7-10 days in separate wells. GPTE and DRG cells then were cocultured for 48 h, and 10 mM bromodeoxyuridine (BrdU), a thymidine analogue, was added in the final 24 h. Control GPTE cells were grown under similar conditions but without DRG cells. Coculture with DRG cells stimulated GPTE cell traversal of S phase. BrdU labeling in cocultured GPTE cells was 42.8 +/- 5.8 compared with 18.1 +/- 7.2% in control GPTE cells (P < 0.001, n = 6). Coculture in the presence of either the neurokinin (NK)1 receptor antagonists LY-297911 or CP-99,994, the NK2 receptor antagonist SR-48,968, or the calcitonin gene-related peptide (CGRP) receptor antagonist hCGRP-(8-37) (10(-7) M of each) during coculture attenuated proliferation of GPTE cells. Treatment with all three antagonists together during coculture decreased BrdU labeling to 2.4 +/- 0.9% of labeled cells vs. 8.5 +/- 0.5% of labeled cells during coculture without antagonists (n = 4, P < 0.02). DRG cells in coculture secreted substantial concentrations of CGRP [71.0 +/- 11.3 (+/- SE) pmol/ml], substance P (1.26 +/- 0.35 pmol/ml), and neurokinin A (0.45 +/- 0.10 pmol/ml) (n = 19 for each).(ABSTRACT TRUNCATED AT 250 WORDS)