Modeling of BK and SK currents in SN DA neurons.

<p>(A). Model of the BK current in SN DA neurons. Left Panel. Activation functions were obtained as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0051610#pone-0051610-g009" target="_blank">figure 9F</a>, shown here for clarity. Activation function and time constant of the BK currents fit to the rising phase of the experimental currents were fit using <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0051610#pone.0051610.e174" target="_blank">eqs. (1)</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0051610#pone.0051610.e175" target="_blank">(2)</a> with ms, ms and V and K as defined in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0051610#pone-0051610-g009" target="_blank">figure 9F</a>. Right Panel. BK currents generated using the MATHEMATICA NDSolve function. The calcium concentration was solved in parallel for this currents using a procedure similar to the one described in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0051610#pone-0051610-g011" target="_blank">figure 11</a>. (B) <i>Model of the SK current in SN DA neurons</i>. Left Panel. Activation function estimated from the fit to experimental currents using <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0051610#pone.0051610.e209" target="_blank">Eq.(4)</a>, where K = 0.01 mM. Middle panel. Time constant of activation for SK currents were directly derived from the fit to the experimental currents. This time constant is voltage-independent consistent with the voltage-independent activation postulated for this current. ms. Right Panel. SK currents generated using a MATHEMATICA protocol similar to the one described in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0051610#pone-0051610-g011" target="_blank">figure 11</a>. (C) Left panel. Currents obtained from a P4 neuron in response to depolarizing voltage pulses (Same as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0051610#pone-0051610-g003" target="_blank">figure 3A</a>, left). TTX used to block channels. Right panel. Model neuron incorporating the <b><i>I_A</i></b>, <b><i>BK</i></b>, and <b><i>SK</i></b> currents in response to depolarizing voltage pulses. No attempt made at fitting exactly the curves and this panel shows in a qualitative sense how the model approximates a typical outward current recording from a SN DA neuron.