Effect of extracellular Ca²⁺ removal, nifedipine, CPA, and ryanodine on PMA-induced Ca²⁺ oscillations. Ca²⁺ oscillations in single airway SMCs induced by 10 µM PMA (added 30 min before the recording started) and its inhibition by: (A) superfusion with Ca²⁺-free sHBSS, (B) 10 µM nifedipine, (C) 10 µM CPA, or (D) 25 µM ryanodine. Each trace is representative of four experiments in lung slices from three mice.