Suppression of the light response by RuR. (A) A Joseph cell voltage clamped at −50 mV was stimulated with flashes of light (2.2 × 1011 photons × s−1cm−2) in ASW during superfusion with 5 µM RuR and after returning to control condition. The photocurrent was reversibly attenuated. (B) Time course of the effect of RuR. The peak amplitude of the light-evoked current is plotted as a function of time for the three phases of the experiment. (C) Intensity series measured in a different Joseph cell in control conditions and in the presence of 5 µM RuR. In the presence of the antagonist, large photocurrents could still be elicited when light intensity was increased. (D) Shift in sensitivity induced by RuR. The normalized peak amplitude of the photocurrent is plotted as a function of light attenuation in the two conditions. A substantial right shift of the stimulus–response curve was induced by RuR. Unattenuated light intensity: 5.1 × 1014 photons × s−1cm−2.
