Before revision: A thirteen-state master equation for Na+ channel gating that describes the coupling between three activation sensors, a two-stage fast inactivation process and a slow inactivated state , may be reduced to kinetic equations for a six state system . Assuming that the activation sensors are independent and that activation has a faster relaxation than inactivation , the fast inactivation rate function is, in general, dependent on the activation variable m(t) but may be approximated by a voltage-dependent function, and the rate function for entry into the slow inactivated state is dependent on the fast inactivation variable .
After revision: A thirteen-state master equation for Na+ channel gating that describes the coupling between three activation sensors, a two-stage fast inactivation process and a slow inactivated state , may be reduced to kinetic equations for a six state system by application of the method of multiple scales. By expressing the occupation probabilities for closed states and the open state in terms of activation and fast inactivation variables, and assuming that activation has a faster relaxation than inactivation , the fast inactivation rate function is, in general, dependent on the activation variable m(t) but may be approximated by a voltage-dependent function, and the rate function for entry into the slow inactivated state is dependent on the fast inactivation variable .