The role of neurokinin A and calcitonin gene-related peptide in the mucociliary defence of the rabbit maxillary sinus.

Substance P (SP) released from sensory C-fibres in the airways increases the mucociliary (m.c.) activity in the rabbit maxillary sinus. The purpose of the present study was to investigate the m.c. effects of two other neuropeptides, coexisting with SP in sensory neurones, neurokinin A (NKA) and calcitonin gene-related peptide (CGRP). NKA increased the m.c. activity dose-dependently (dose range 0.1-5.0 micrograms/kg) the maximum increase being 33.6 +/- 6.0%. The effect was inhibited by pretreatment with the tachykinin antagonist (D-Pro2, D-Trp7,9)SP, but not with atropine or hexamethonium. Thus NKA released from sensory C-fibres may contribute to the non-cholinergic increase of m.c. activity observed after C-fibre stimulation. In contrast CGRP did not influence the m.c. activity. Neither did it influence the responses to NKA or SP. It is concluded that CGRP is unlikely to be involved in the control of m.c. function.