You are studying a neuron which you discover has a new kind

You are studying a neuron which you discover has a new kind of channel. The channel is a voltage-gated chloride channel with a threshold for opening of around -40 mV, similar to other voltage-gated channels. The intracellular chloride concentration is 100 mM, the extracellular chloride concentration is 10 mM. The cell is at room temperature. What is the chloride equilibrium potential? Draw the IV curve for this voltage gated chloride channel. You discover that the voltage gated chloride channel shows inactivation with the same time course as a normal voltage gated sodium channel. If a neuron has these voltage-gated chloride channels along with standard voltage-gated potassium channels, but no voltage-gated sodium channel can it still fire action potentials? Why or why not?

Solution

1) The equilibrium potential can be determined using the Nernst Equation

V_Eq = RT/zF ln(X_out/X_in) Where R - gas constant (8.314 J.K^-1.mol^-1); T - Temperature in kelvin (K = °C + 273.15); z - valence of the ionic species.Cl^-; F - Faraday\'s constant (96485 C.mol^-1); X_out - concentration of the ionic species X in the extracellular fluid. X_in - concentration of the ionic species X in the intracellular fluid.

By substituting we have

The chloride equilibrium potential is -59 mV.