Overview of microdialysis

Abstract

The technique of microdialysis enables the monitoring of neurotransmitters and other molecules in the extracellular environment. This method has undergone several modifications and is now widely used for sampling and quantitating neurotransmitters, neuropeptides, and hormones in the brain and periphery. This unit describes the principles of conventional and quantitative microdialysis as well as strategies in designing a dialysis experiment. It establishes the groundwork for the basic techniques of preparation, conduct, and analysis of dialysis experiments in rodents and subhuman primates. Although the methods described are those used for monitoring CNS function, they can be easily applied with minor modification to other organ systems.

Figure 7.1.1

Representation of the “inside view” of a microdialysis probe. The microdialysis probe, which consists of an inflow and outflow tubing (A) separated by tubing made of dialysis membrane, is implanted surgically into a specific area within the brain (B). The enlarged view (C) illustrates the complex composition of the fluid through which analytes (black dots) must diffuse to get to the microdialysis probe. The presence of impermeable cells such as blood vessels (V) reduces the fluid volume surrounding the probe and increases the diffusional path (arrow) of analytes moving toward the probe. The net effect is a decreased diffusivity in this phase.