Microdialysis and its use in behavioural studies: Focus on acetylcholine.

Microdialysis is a technique that allows access to the extracellular space of many tissues. For behavioural studies, microdialysis probes are inserted into the brain under anesthesia, but the experiment can be done in awake and freely moving animals. Microdialysis is a sampling method (not a measuring method), therefore, the analyte(s) under study must be quantified from the dialysate using available analytical methods of high sensitivity. Neurotransmitters and energy metabolites are most commonly measured. Limitations of the microdialysis technique are poor time resolution in the minute range and large diameters of the probe which samples from many thousands of cells and millions of synapses. The article illustrates the use of microdialysis in several behavioural fields and describes uses in motor function, stress research, and novelty and habituation, with an emphasis on its use in cholinergic mechanisms.