Sensory nerves in the airways as a target for drug development

1. Electrical stimulation (2.5-10 Hz, 80 V, 1 ms for 15 s) within the spinal canal of the pithed guinea-pig pretreated with atropine, D-tubocurarine and pentolinium caused a bronchoconstrictor response, indicated by a rise of insufflation pressure. 2. The magnitude of these non-cholinergic neuronal bronchoconstrictor responses were frequency-dependent, capsaicin-sensitive and temperature-dependent. 3. Responses could be inhibited by the alpha 2-adrenoceptor agonist B-HT920 (3 mg/kg, i.v.) and the mu-opioid agonist H-Tyr-D-Arg-Phe-Lys-NH2 (DALDA; 1 mg/kg, i.v.) and the attenuation observed could be overcome by use of the respective antagonists idazoxan (3 mg/kg, i.v.) and naloxone (3 mg/kg, i.v.). 4. Substance P-induced bronchoconstriction (0.3 micrograms/kg, i.v.), but not that due to electrical stimulation, was attenuated by indomethacin (3 mg/kg, i.v.), indicating an indirect action of substance P via a product of arachidonic acid metabolism. 5. The prostanoid product of the substance P response was probably thromboxane A2. 6. Hence, novel drug development could be directed towards tachykinin receptors or to the synthesis, release and degradation of neuropeptides.