The provided code models the kinetics of a specific ion channel current in neurons, specifically the slowly inactivating delayed potassium current. This model is based on parameters from Schild's 1994 study and is intended to simulate the biophysical properties of neuronal membrane channels that conduct this current.
The code is modeling potassium ion (K⁺) channels, which are crucial for maintaining the resting membrane potential and shaping action potentials in neurons. The specific current modeled here is a slowly inactivating delayed rectifier potassium current, sometimes referred to as Kds. This current plays a role in repolarizing the membrane after an action potential and in modulating neuronal excitability.
The model incorporates gating variables (x and y1) that represent the probability of the potassium channel being in an open or closed state. The transition between these states is voltage-dependent and influenced by factors like membrane potential (v) and specific midpoint voltages (e.g., V0p5x and V0p5y), which determine the voltage at which half of the channels are activated or inactivated.
The model includes a temperature coefficient (Q10kds), which accounts for the effect of temperature on the channel kinetics. Q10 is a common biological parameter that quantifies the rate of change of a biological process with a 10°C change in temperature. Here, it adjusts the kinetic rates of the gating variables when simulating conditions at body temperature (37°C), although original parameters are for 22°C.
The model captures the voltage-dependent nature of channel gating through factors such as xinf and yinf, which are steady-state activation and inactivation values, respectively. These are functions of the membrane voltage and specific parameters from the empirical study by Schild.
The conductance of the channel, represented as g, is calculated based on the maximal conductance (gbar) and the states of the gating variables. This conductance determines the potassium current (ik), which is crucial for its role in neuronal signaling.
Overall, the code models the biophysics of a slowly inactivating potassium current in neurons by incorporating parameters such as gating kinetics, temperature dependence, and voltage sensitivity. The model provides a mathematical framework to simulate the contribution of this current to neuronal excitability and membrane potential dynamics, drawing from empirical data. This type of modeling helps in understanding the roles different ion channels play in the physiological behavior of neurons.