Fig. 5.

The inhibitory effect of SRIF on high voltage-activated Ca²⁺ currents in rods. The test solution contained 0 CaCl₂ and 20 mmBaCl₂ substituted for equimolar NaCl. a, A depolarizing step to 0 mV from a holding potential of −70 mV was applied to record whole-cell Ca²⁺ current in control external solution (1), after a 1 min exposure to 0.2 μm SRIF (2), and after a wash (3).b, The I–V relationship of Ca²⁺ currents evoked by depolarizing voltage steps from −50 to +50 mV in 10 mV increments in the absence (opencircles) and the presence of 0.2 μm SRIF (closedcircles) is shown. c, The time course of SRIF blockade was evaluated by applying 70 msec depolarizing pulses to a test potential of 0 mV from a holding potential of −70 mV each 5 sec. The time of SRIF application is shown by the hatchedhorizontalbar. Thenumbers correspond to the traces ina.