Figure 4. Comparison of inhibitory effects of DAMGO (10 sup -5 M) and U-50488 H (10 sup -5 M) on electrical field stimulation-induced contractions between 64 trachealis strips (left) and 68 bronchial rings of 3-mm inner diameter (right). The data for the trachealis strips were obtained in this laboratory by similar methods. [9] U-50488 H had a significantly (P < 0.001) larger effect in trachealis strips and DAMGO had a significantly (P < 0.001) larger effect in bronchial rings. In the trachealis strips or bronchial rings, DPDPE had no effect. In general, the conclusions of this comparison were confirmed for DAMGO (10 sup -5 M) and U-50488 H (10 sup -5 M) in additional studies in which eight trachealis strips and eight bronchial rings were sampled from the same animals.