Optimized values of rate constants and gating modifier variables used in the simulations shown in Figure 8.

Gating parameters were estimated using time course fitting of HCN2 currents while those describing Mg2+ block kinetics were derived from block in the presence of cAMP as shown in figures 4 and 5 (see methods for details). Where plus or minus cAMP parameter windows are left blank, the values are constrained to be equivalent to that shown in the other condition for that model. Superscripted #'s refer to the appropriate equations in the methods that were used to determine the value of the indicated parameter.