Experiments to characterize the neurokinin A (NKA)-induced response of mucosal strips. (a) The concentration–response curve to the NKA analogue [Lys5,MeLeu9,Nle10]NKA(4–10) was very similar to that of NKA (both n=6). (b) Preincubation with NK1 receptor antagonist, SR140333 (100 nM), had no effect on the NKA-mediated mucosal response (n=5). (c) Tetrodotoxin (TTX) and (d) indomethacin preincubation (both 1 μM, n=8) resulted in no significant change in responses to NKA in mucosal strips (Student's paired t-test). (e) Responses to NKA in mucosal strips, measured as percentage of maximal carbachol response, were reduced in the presence of SR48968 at 1, 3 and 10 nM, compared with the control (n=4–6). (f) Schild plot of the data in (e). Slope 1.06±0.46; pKB 9.85.