2.2. Microdialysis

Briefly, microdialysis is a catheter-based method allowing for continuous sampling of molecules from the extracellular fluid in the tissue of interest by means of a semipermeable membrane at the tip of the microdialysis catheter (Muller, 2002; Joukhadar and Muller, 2005). The solution that passes through the catheter can be sampled in small vials for subsequent analysis. The microdialysis setup comprised of CMA 107 precision pumps (μ-Dialysis AB, Stockholm, Sweden) and CMA 70 catheters (molecular cut-off 20 kDa). All the microdialysis catheters were perfused with 0.9% NaCl at a perfusion rate of 1 μL/min throughout the sampling periods. Given the continuous perfusion of the microdialysis system, complete concentration equilibrium across the semipermeable membrane will never occur. Thus, the concentration in the dialysate represents only a fraction of the absolute tissue concentration, expressed as relative recovery. A detailed description of microdialysis can be found elsewhere (Muller, 2002; Joukhadar and Muller, 2005; Hanberg et al., 2020).