Figure 1. Effect of intracellular cAMP-ATP on the Ca²⁺-dependent secretory response of rat melanotrophs measured as a change in membrane capacitance (C_m).

The time courses of C_m following intracellular dialysis with 0.45 μm Ca²⁺ alone in control (A), in the added presence of 1 mM ATP (B) and in the added presence of 0.2 mM cAMP and 1 mM ATP (C) are shown. The membrane holding potential was -70 mV in all these experiments.