Immunoblockade by a specific tachykinin antiserum of the non-cholinergic contractile responses in the guinea-pig isolated bronchus.

1. In the guinea-pig isolated bronchus, capsaicin produced a concentration-dependent contraction which was tetrodotoxin- (1 microM) resistant but abolished by previous exposure to capsaicin. 2. Previous incubation with E7 antiserum (which crossreacts with neurokinin A but not with substance P), but not with control rabbit serum, strongly inhibited the contractile response to capsaicin. 3. The E7 antiserum shifted to the right the concentration-response curve to exogenous neurokinin A but not that to substance P. 4. The E7 antiserum also inhibited the non-cholinergic, slowly developing contraction produced by electrical field stimulation (1-5 Hz). 5. These findings provide additional evidence that tachykinin-like peptides play a major role in the bronchoconstrictor response produced by transmitter secretion from peripheral endings of capsaicin-sensitive afferents in guinea-pig bronchi evoked either by capsaicin or by electrical field stimulation.