Fig. 3.

Prolonged inhibition of phosphodiesterases does not block or alter the kinetics of the agonist response.A, Comparison of the amplitude of the agonist (l-APB or glutamate) after 10 min of dialysis with no cGMP, with cGMP, or with solutions designed to inhibit cGMP phosphodiesterase. Responses under all conditions continued to be significantly greater than control (p < 0.01, unpaired t test). B, Glutamate responses after 30 sec and 15 min of recording in On bipolar cells dialyzed with 500 μm GTP, 1 mm cGMP, and 250 μm IBMX (left) and in another cell dialyzed with 500 μm GTP and 250 μm8-pCPT-cGMP (right). Glutamate was applied, after a 2 sec delay, for a period of 5 sec (indicated by the continuous line). In each panel the amplitude of the response after 15 min (thin line traces) was scaled to the response after 30 sec of dialysis (thick line trace). The kinetics of the agonist response, at this degree of temporal resolution, are unchanged by prolonged dialysis with either IBMX or 8-pCPT-cGMP.