Coupled HPLC, capillary electrophoresis, or LC-MS/MS quantification of dialysate fractions
measures
Free (protein-unbound) interstitial concentrations of neurotransmitters and drugs over time
format
Semipermeable hollow-fiber membrane probe (~200–300 μm diameter) continuously perfused with artificial CSF or Ringer solution
pioneer
Evolved from push-pull cannulas (1960s) to continuously perfused dialytrodes (1972) and hollow-fiber probes (1974)
Core Principles & Analysis
A concentric needle probe tipped with a semipermeable hollow-fiber membrane (~200–300 μm diameter) is stereotaxically implanted into brain regions or peripheral tissues and continuously perfused with physiological buffer.
Because the membrane molecular-weight cutoff excludes proteins and enzymes, microdialysis selectively samples only the pharmacologically active, unbound fraction of drugs and endogenous neurotransmitters (dopamine, serotonin, glutamate, GABA, acetylcholine).
In the no-net-flux calibration method, perfusing the probe with several known concentrations of analyte and plotting the dialysate difference (Cout − Cin) against Cin determines both probe recovery and the true steady-state extracellular concentration.