Exercise and Neurotransmission: A Window to the Future?

Peripheral physiological adaptations to exercise have been the subject of several studies. To adjust to the disturbance in resting homeostasis induced by the exercise stimulus, a number of regulatory systems are called upon to return the body to a new level of homeostasis. In contrast with our knowledge about the peripheral adaptations to exercise, studies relating exercise to brain neurotransmitter levels are scarce. It is of interest to examine the effect of acute and chronic exercise on neurotransmitter release, since movement initiation and control of locomotion have been shown to be related to striatal neurotransmitter function. One of the possible therapeutic modalities in movement and mental disorders is exercise therapy. But also chronic adaptations to training and disturbances caused by overtraining might be reflected in brain functioning. 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. Although there are great discrepancies in experimental protocols, the results indicate that there is evidence in favor of changes in synthesis and metabolism of monoamines during exercise. In previous studies, we used the microdialysis technique to monitor the release of neurotransmitters in different brain nuclei during exercise. We have shown that DA, NA, and 5-HT release is increased during exercise. We also showed that acute exercise and/or exercise training influences extracellular DA, NA, GLU, and GABA levels. Taken together this could indicate that chronic disturbance of homeostasis could also influence transmitter release and that this paradigm could serve as a tool to explore the central effects of overtraining.