Figure 2.

Effects of photolysis of 5cgY-RS-20 on Ca²⁺ current enhancement and shortening in Bufo marinus smooth muscle cells. (A) Voltage clamp protocol used to demonstrate enhancement of inward Ca²⁺ currents (I_Ca) by repetitive depolarization of single smooth muscle cells. (B and C) Currents during initial 3-sec depolarizations before (T₁) and 12 sec after the train (T₂) are shown for an experiment in which 200 μM 5cgY-RS-20 or 200 μM caged tyrosine (cgY) were included in the pipette. The protocol was carried out on each cell before (Left) and just after (Right) 15-sec exposure to a xenon source UG11 filtered to pass near-UV light. (D) Summary of the effect of 5cgY-RS-20 and cgY on enhancement of inward Ca²⁺ current. The mean (± SEM) peak inward current after versus before the conditioning train (T₂/T₁) is shown for seven and five cells with 5cgY-RS-20 and cgY, respectively. (E) Images of a smooth muscle cell attached to a pipette containing 200 μM 5cgY-RS-20 in the whole-cell configuration. Images were observed just before and 1 and 3 sec after depolarization with the train of pulses shown in A. (F) Same cell as in E but after illumination to release 5Y-RS-20. (G) Mean (± SEM) rates of shortening of four cells before and after photorelease of 5Y-RS-20.