FIGURE 2.

Real-time kinetic modeling of voltage-gated channels using dynamic clamp. The procedure is based on minimizing the difference between two action potential waveforms: one obtained under control conditions (A), and the other (B) obtained by replacing the current of the studied voltage-gated channel, using the dynamic-clamp engine (C), as shown in Fig. 1. The minimization of the cost function (the MSE between the two AP waveforms) can be done manually or programmatically (F), by changing in real time the parameters of a voltage-dependent kinetic model (D). A parameter-dependent penalty can be optionally added to the cost function, to include a priori knowledge, such as that provided by macroscopic currents (G) previously recorded from the same or other cell(s). Both the control and the fitted AP waveforms are averages of multiple consecutive spikes, detected when V_m crosses a user-defined threshold, e.g., −30 mV (E). The computation is divided between several parallel threads, but only the dynamic-clamp thread (C) runs in real time, responding within dt to any change in parameters, via manual user input, or from the optimizer.