The chloride concentration in the ACSF used in the lab is 131.5 mM, while the concentration in the internal solution used to fill patch electrodes is 4.4 mM. Assume that you are making a whole cell current clamp recording from a cell using these solutions. You are recording at room temperature (20oC) and have determined that your cell has a resting potential of -70 mV.
A. What is the chloride reversal potential? Show your work.
B. If you suddenly add GABA to the bath, will GABA depolarize, hyperpolarize, or not alter the membrane potential? Explain.
C. Is there a net movement of chloride into or out of the cell when you add GABA to the bath? If so, in which direction?
D. Suppose you switch your internal solution to one containing 25 mM chloride and obtain a whole cell recording from a new cell that is also resting at -70 mV. What effect will the addition of GABA to the bath have on the membrane potential of this cell? On the net direction of chloride movement into or out of the cell?