Fig. 4.

Capsaicin-mediated contraction of guinea pig tracheal rings. A: representative tracings of 10 µM capsaicin-induced contraction of tracheal rings in the presence of 1 µM tetrodotoxin, 100 µM Na⁺-channel inhibitor bupivacaine, 20 µM NK-2 receptor antagonist GR-159897, or vehicle. B: quantification of capsaicin-induced contraction force as a fraction of 100 µM acetylcholine-induced force. Pretreatment with bupivacaine and GR-159897 significantly inhibited contraction force. Values are means ± SE; n = 4 for all groups. *P < 0.05 compared with untreated controls by ANOVA with Bonferroni post hoc correction.