A, changes in the cGMP sensitivity after excision of membrane patches containing CNGA1Y498F/CNGB1 channels in the presence of a PTP inhibitor, vanadate (100 μM). B, changes in the cGMP sensitivity after excision of membrane patches containing CNGA1Y498F/CNGB1 channels in the presence of erbstatin (25 μM), a PTK inhibitor, and/or 500 μM ATP.