A high concentration of sucrose is applied to the extracellular space, which prevents the correct opening and closing of sodium and potassium channels, increasing resistance between two groups of cells.
[2] The sucrose gap technique was first introduced by Robert Stämpfli [de] in 1954[3] who worked with Alan Hodgkin and Andrew Huxley between 1947 and 1949.
From his research, Stämpfli determined that currents moving along nerve fibers can be measured more easily when there is a gap of high resistance that reduces the amount of conducting medium outside of the cell.
[6] 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.
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.
The method creates conduction block in a nerve or muscle fiber by introducing a gap of high resistance between two groups of cells.
[9] When used with proper electronics, the double sucrose gap can be used to voltage clamp the membrane potential of the nerve or tissue segment contained in the test chamber.
It is very complicated, however, to achieve similar measurements with intracellular or patch-clamp electrodes because they can physically damage small axons or cells.
This method is also useful in studying the changes in membrane potential in response to different pharmacologically active agents, which can be introduced in the test chamber.
[7] Also, the sucrose solution, which has a low ionic concentration, can deplete the exposed cells of vital intracellular ions such as sodium and potassium, which can affect their viability.
[7] Studies on the effects of choline, acetylcholine, and carbachol on the resting potentials of the superior cervical ganglion in rabbits were conducted using the sucrose-gap method.
[10] The sucrose-gap technique has been applied to determine the relation between external potassium concentration and the membrane potential of smooth muscle cells using guinea-pig ureters.