Figure 1.

Effect of injection of Ca²⁺/calmodulin-binding peptides CMKII 290–309 and VIP into Limulus ventral photoreceptors. (A) Effects of intracellular pressure injection of CMKII 290–309 on the light-induced current. At the top is a continuous current trace (100-s scale bar). A dim light flash every 30 s induced inward current (downward deflection). During the period marked “CMKII 290–309,” the peptide was injected with multiple, small pressure pulses. This produced a large, but reversible decrease in the light response. Directly underneath are response averages (n = 5, 200-ms scale bar) during periods indicated by the bars and arrows. Solid rectangles represent the flash. Voltage (V) and current traces (I) are as indicated. (B) Effect of control peptide on the light-induced current. Approximately twice the number of injections of similar volume were made than in A. (C) Effect of VIP injection on the light-induced current. Single responses are shown before injection, immediately following, 10 s later, and 20 s later.