Fig. 6.

8MM-IBMX sensitive PDE activity does not effectively hydrolyze 5 μM cAMP washed in from the patch pipette. The wash in of 5 μM cAMP was monitored with C460W/E583M channels. Wash in of 5 μM cAMP caused a steady increase in current through CNG channels. Current levels reached a plateau in ∼400 s. Exposure to 100 μM 8MM-IBMX did not trigger an additional increase in current through CNG channels. Addition of 10 μM rolipram caused a substantial increase in current. These data indicate the 8MM-IBMX-sensitive PDE activity in HEK-293 cells is not sufficient to alter the cAMP levels that reached CNG channels.