Stochastic resonance of ELF-EMF in voltage-gated channels: the case of the cardiac I_Ks potassium channel

We applied a periodic magnetic field of frequency 16 Hz and amplitude 16 nT to a human IKS channel, expressed in a Xenopus oocyte and varied the membrane depolarization between -100 mV and +100 mV. We observed a maximal increase of about 9% in the potassium current at membrane depolarization between 0 mV and 8 mV (see Figure 3). A similar measurement of the potassium current in the KCNQ1 channel, expressed in an oocyte, gave a maximal increase of 16% at the same applied magnetic field and membrane depolarization between -14 mV and -7 mV (see Figure 4). We attribute this resonant behavior to stochastic resonance between the thermal activations of the configuration of interacting ions in the IKs channel over a low potential barrier inside the closed state of the channel and the periodic electromotive force induced across the membrane by the periodic magnetic field. The partial synchronization of the random jumps with the periodic force changes the relative times spent on either side of the barrier, thereby changing the open probability of the spontaneously gating open channel. This, in turn, changes the conductance of the channel at the particular Partially supported by a research grant from the Adams Brain Research Center, Tel-Aviv University Partially supported by research grants from the Israel Science Foundation and the US-Israel Bi-national Science Foundation