Figure 8.

Role of extracellular Ca²⁺ during the contraction and the Ca²⁺ signaling of airway SMCs induced by 5-HT and ACH. (A and B) Contractile responses of airways in different lung slices sequentially exposed (top bars) to 1 μM 5-HT and 1 μM ACH in the presence or absence of extracellular Ca²⁺. Representative traces of five airways from three mice. (C–H) The changes in [Ca²⁺]_i in small ROIs of single SMCs were determined in lung slices stimulated with (C, E, and G) 1 μM 5-HT or (D, F, and H) 1 μM ACH in the (C and D) presence or (E and F) absence of extracellular Ca²⁺ as indicated by top bars. In the absence or presence of extracellular Ca²⁺, both agonists induced an increase in [Ca²⁺]_i followed by Ca²⁺ oscillations. Although Ca²⁺ oscillations persisted in the presence of extracellular Ca²⁺, they progressively reduce their frequency and stopped in the absence of extracellular Ca²⁺. (G and H) The frequency of agonist-induced Ca²⁺ oscillations, calculated every 20 s, in the presence (squares) or absence of Ca²⁺ (triangles) with respect to time. Symbols and bars are the mean ± SEM of five to eight SMCs in five paired experiments from different lung slices from three mice.