Figure 1: Principle of microdialysis technique: The most important element of the technique is the microdialysis probe (left side). The probe is introduced into the target tissue where the free molecules in the ECF can diffuse through the probe membrane into the perfusion solution (right side). The cut off value of the probe membrane limits the size of the molecules diffusing through the membrane. For quantitative microdialysis calibrator molecules can be perfused through the probe and the loss of their concentrations in the dialysates can be measured. The recovery of the probe for a specific test substance can be calculated.