Figure 3.

Kinetics of current recovery to baseline in 0 Ca²⁺ Ringer. Current responses induced by photorelease of 8-Br-cAMP as a function of flash intensity in 0 Ca²⁺ Ringer. Holding potential was −50 mV. Flashes of increasing relative intensities 0.01, 0.1, 0.32, 0.5, 0.8, 1 were applied to the ciliary region. In this neuron, the maximal current response, entirely due to activation of CNG channels, was already reached at 0.5 relative light intensity. Higher light intensities elicited the same peak current, but increased the time necessary for the current to return to baseline, probably due to the time employed by 8-Br-cAMP to diffuse away from the cilia. The increase in recovery time with higher light intensity indicates that although the CNG current was already fully activated, the intraciliary concentration of 8-Br-cAMP could be further increased, meaning that with a pipette concentration of 50 μM caged 8-Br-cAMP, the range of light intensity of our experimental system could fully activate the CNG channels.