FIGURE 3.

cAMP induced activation of SpIH channels. I_m elicited by hyperpolarizing pulses (A) (from -20 to -120 mV) in SpIH transfected HeLaCx43 cells in with both 2 mM Ca²⁺ (B) and with no added Ca²⁺ (C). Schematics in the right panels of (B) and (C) illustrate the experimental conditions. In both cases the external KAsp bath solution contained 500 μM cAMP. I_m increased significantly with V_m and hyperpolarization induced voltage- and time-dependent inward currents when no external Ca²⁺ was present. (D) Average of current amplitudes recorded in the presence and in the absence of external Ca²⁺, respectively: 6.4 ± 1.1 pA/pF, n = 10 versus 39.5 ± 5.8 pA/pF, n = 13; P < 0.001.