Figure 6.

Effect of Ca²⁺-modulators on the response to ACh. (A) As visible from the representative current trace, application of the Ca²⁺-ionophore A23187 (2 µM, luminal) to the mouse tracheal epithelium led to a transient current increase. Addition of 100 µM ACh (luminal) in the presence of A23187 did not change the course of the current. (B) Application of A23187 led to a significant transient increase in the I_SC (n= 5, P < 0.05). No significant response to ACh occurred in the presence of A23187 (n= 5, P= 0.12). (C) Luminal application of 75 µM of the IP₃-receptor antagonist 2-APB led to a current decrease. Additional application of 100 µM ACh led to a current increase consisting of a transient peak. (D) Statistical analysis revealed that 2-APB significantly reduced the transient ACh-induced peak current (n= 5, P < 0.05) and abolished the plateau component.