Brain microdialysis and its application for the study of neurotransmitter release during exercise

Physical exercise influences the central dopaminergic, noradrenergic, and serotonergic systems. A number of studies have examined brain noradrenaline (NA), serotonin (5‐hydroxytryptamine, or 5‐HT), and dopamine (DA) with exercise. The microdialysis technique employs the dialysis (from Greek: to separate) principle in which a membrane, permeable to water and small solutes, separates two fluid compartments; microdialysis can collect virtually any substance from the brains of freely moving animals with a limited amount of tissue trauma. This method allows the measurement of local neurotransmitter release in combination with on‐going behavioral changes such as exercise. Several kinds of behavior have been studied using microdialysis. The first studies were descriptive, i.e., they registered the extracellular neurotransmitter concentrations during locomotion or after application of an acute stress. Thereafter, the effects of acute and chronic stress, such as an acute bout of endurance exercise or training, on extracellular neurotransmitter concentrations were evaluated both at rest and during exercise. The latest studies evaluated the link between extracellular neurotransmitter concentrations and fatigue in running animals and their direct effect on peripheral hormonal concentrations and on the regulation of body temperature during exercise. The present paper will discuss the application of microdialysis in neuroscience, focusing on exercise and behavioral‐related studies