Figure 8. Pharmacological properties of I_HA and I_DA.

A, 5 min treatment with 30 μm CPA failed to induce an inward I_HA (left) or I_DA (right) in 2.5 mm Ca²⁺, high-Na⁺ external solution (n = 5), but both currents were readily activated following Ca²⁺ removal. Note that at positive potentials current could be activated by CPA. B, SK&F 96365 at concentrations of up to 100 μm did not inhibit inward I_HA (left), but completely abolished I_DA (right) in the same cell (n = 7). Current at positive potentials at which it could be activated by CPA (left panel in A) was also inhibited by SK&F 96365. C and D, I_DA (right) was more sensitive to the inhibitory action of Gd³⁺ or La³⁺ compared to I_HA (left) but both currents were abolished by 100 μm of either blocker. In all panels I_HA and I_DA were measured in the same cells.