Fig. 6.

MCh-induced Ca²⁺ signaling in rat and mouse airway SMCs before and after treatment with caffeine and ryanodine (Caff/Rya). These representative traces show that MCh induced Ca²⁺ oscillations before caffeine/ryanodine treatment. Exposure to caffeine/ryanodine to create a Ca²⁺-permeabilized lung slice induced a fast elevation of intracellular calcium concentration ([Ca²⁺]_i) in the SMCs, which subsequently stabilized and remained at a high level when caffeine/ryanodine was removed. A 2nd exposure to caffeine/ryanodine or MCh had no further effect on the [Ca²⁺]_i. However, [Ca²⁺]_i dropped significantly when the extracellular Ca²⁺ was removed and was elevated to the previous level when extracellular Ca²⁺ was replaced. The responses were similar in rat and mouse airway SMCs.