Sensitivity of PMA-induced Ca²⁺ oscillations and SMC twitching to inhibition of PKC or ROK. The effect of PKC inhibitor GF-109203X (1 µM) or ROK inhibitor Y-27632 (10 µM) on (A and B) Ca²⁺ oscillations in single airway SMCs and (C and D) SMC twitching in the airway wall induced by 10 µM PMA (added 30 min before the recordings started). Line scans showing SMC twitching were obtained from a small region on the airway wall from phase-contrast images (as illustrated in Fig. 1). PMA-induced Ca²⁺ oscillations and SMC twitching (striated white lines) were inhibited (straight white lines) by GF-109203X but not by Y-27632. Each experiment is representative of six airways in lung slices from three mice.