Method
A classic sucrose gap technique is typically set up with three chambers that each contain a segment of the neuron or cells that are being studied. The test chamber contains a physiological solution, such as Krebs or Ringer's solution, which mimics the ion concentration and osmotic pressure of the cell's natural environment. Test drugs can also be added to this chamber to study the effect that they have on cellular function. Ag-AgCl or platinum wire electrodes are generally used for stimulating the cells in the test solution. The sucrose chamber (or gap) is the middle chamber that separates the two other chambers, or sections of the nerve fiber or cells. This chamber contains an isotonic sucrose solution of a high specific resistance. Specific resistance describes the ability of a material or solution to oppose electrical current, so a sucrose solution of a high specific resistance is effective in electrically isolating the three chambers. The third chamber usually contains a KCl solution that mimics the intracellular solution. The high potassium concentration in this chamber depolarizes the immersed segment of the tissue, allowing potential differences to be measured between the two segments separated by the sucrose gap. Vaseline, silicon grease, or a silicon-vaseline mixture is used to seal the nerve or tissue in position and prevent diffusion of solution between the chambers. A pair of agar-bridged Ag-AgCl electrodes are placed in the test and KCl chambers to record the changes in membrane potential.
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