Fig. 3. Representative force recordings of guinea pig tracheal ring preparations suspended in organ baths illustrating the effect of various antagonists on the contractile effects of rapacuronium (Rap). After precontraction with acetylcholine (ACh) and three washes, antagonists were added before 1–100 μm rapacuronium. (  A ) Atropine (1 μm) completely inhibited rapacuronium-induced contraction. (  B ) Pyrilamine (10 μm) or (  C ) sendide and MEN10376 (each 30 μm) were without effect on rapacuronium-induced contractions. Conversely, atropine added at the peak of a sustained contraction completely inhibited the rapacuronium-induced contraction. Illustrations are typical of at least three independent experiments for each condition.