The effect of NOC-5 on Ca²⁺ sensitivity of airway SMCs. (A) The effect of 10 µM NOC-5 on Ca²⁺ signaling induced by 0.1 µM 5-HT in the same SMC before (Normal) and after Ca²⁺ permeabilization with 20 mM caffeine and 50 µM ryanodine in sHBSS ([Ca²⁺] = 1.3 mM). Before Ca²⁺ permeabilization, Ca²⁺ oscillations were induced by 5-HT and inhibited by NOC-5. After Ca²⁺ permeabilization, [Ca²⁺]_i was constantly elevated, and neither 5-HT nor NOC-5 induced further changes in [Ca²⁺]_i. (B and C) The response of airways contracted with 0.1 µM 5-HT to (B) 10 µM NOC-5 or (C) 10 µM 8pCPT-cGMP in lung slices before and after Ca²⁺ permeabilization. Both NOC-5 and 8pCPT-cGMP relaxed airways before Ca²⁺ permeabilization, but neither had much effect on airways after Ca²⁺ permeabilization. Contraction data are representative of at least seven different slices from three mice. Ca²⁺ data are representative of three different slices from one mouse.