Changes in PLCδ₁PH-mRFP fluorescence in Ci-VSP–expressing fibers during the train of depolarizing steps protocol. (A) PLCδ₁PH-mRFP fluorescence detected in a fiber successively challenged by the above shown voltage-pulse protocols; fluorescence was measured in line-scan mode. The rightmost trace corresponds to the ratio of the sum of the two traces taken during a test train-pulse protocol and the sum of the two other traces. (B) Mean (±SEM; gray shading) change in fluorescence during the test protocol (n = 4); in each fiber, the fluorescence record during the test protocol was normalized by bracketing traces recorded while either applying no pulse or while applying a control protocol.