Solutions for Patch-Clamp Experiments

Solutions used in patch-clamp can be divided into two general categories by the side of the patch membrane with which the solution is in contact. The compositions of extracellular solutions are usually similar to those of the natural extracellular fluids, whereas intracellular solutions resemble cytosol with respect to pH, free Ca²⁺ , and Mg²⁺ concentrations and ATP content. Designing solutions for patch-clamp experiments requires careful consideration of the physicochemical processes controlling the concentrations of protons and divalent cations, ionic strength, and osmotic pressure. Liquid junction potentials arising at the interfaces between different experimental solutions may contribute to the membrane potential and should be measured or calculated and adequately compensated. This chapter describes general strategies and methods for practical calculations of these parameters, which are critically important for successful patch-clamp experiments.