Photosensitivity of 8BrcGMP‐induced conductance in ROS‐excised patches

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Abstract
Inside‐out patches from ROS plasma membranes contain the basic enzymes of the phototransduction cascade. Similar to a native photoreceptor cell, such patches are capable of responding to light, the effect of which suppresses the cGMP‐activated current. Photoresponses are observed only in the presence of GTP, whereas ATP essentially accelerates the current recovery to a dark level. Photoresponses are also observed in the presence of 8BrcGMP. Phosphodiesterase (PDE) hydrolyzes 8BrcGMP two orders of magnitude slower than cGMP, so the light inhibition of the 8BrcGMP‐induced current cannot be accounted for by PDE activation. It seems that activity of cGMP‐gated channels depends not only on cGMP concentration, but is additionally controlled by some other regulatory mechanisms.