Figure 5.

Inactivation kinetics and dynamic action potential model of atrial gap junctions. A, An example of a whole cell (I₂) current during a voltage clamp step to −110 mV from a single wt atrial myocyte experiment. The fast and slow decay time constants (τ_fast and τ_slow) were determined by exponential curve fitting of the I_j trace. B, A similar example of the decay time constant (τ) curve-fitting and open probability (P_open) measurements for a Cx40KO atrial I_j recording. C, The average fast inactivation rates (k_{on, fast} mean ± s.d., n = 5-8), for wt and Cx40KO atrial G_j increased exponentially with V_j (voltage constant of 18.6-8 mV). D, The average slow inactivation rates (k_{on, slow}) for wt and Cx40KO atrial G_j similarly increased exponentially with a V_j constant (ν) of 18.1-6 mV. E, Dynamic gap junction model fit of time-dependent wt atrial G_j curve during the BCL = 1 sec ventricular action potential using the kinetic inactivation parameters from panels C and D. The wt atrial G_j model is similar to the previously described ventricular G_j model except that the inactivation kinetics were slower and the early recovery commences sooner [15]. F, Dynamic gap junction model fit of time-dependent Cx40KO atrial G_j curve during the same model ventricular action potential. The Cx40KO atrium had faster inactivation kinetics and slightly more late recovery (R₂) than wt atrial G_j