Physical exercise-induced fatigue: the role of serotonergic and dopaminergic systems

Brain serotonin and dopamine are neurotransmitters related to fatigue, a feeling that leads to reduced intensity or interruption of physical exercises, thereby regulating performance. The present review aims to present advances on the understanding of fatigue, which has recently been proposed as a defense mechanism instead of a "physiological failure" in the context of prolonged (aerobic) exercises. We also present recent advances on the association between serotonin, dopamine and fatigue. Experiments with rodents, which allow direct manipulation of brain serotonin and dopamine during exercise, clearly indicate that increased serotoninergic activity reduces performance, while increased dopaminergic activity is associated with increased performance. Nevertheless, experiments with humans, particularly those involving nutritional supplementation or pharmacological manipulations, have yielded conflicting results on the relationship between serotonin, dopamine and fatigue. The only clear and reproducible effect observed in humans is increased performance in hot environments after treatment with inhibitors of dopamine reuptake. Because the serotonergic and dopaminergic systems interact with each other, the serotonin-to-dopamine ratio seems to be more relevant for determining fatigue than analyzing or manipulating only one of the two transmitters. Finally, physical training protocols induce neuroplasticity, thus modulating the action of these neurotransmitters in order to improve physical performance.

[A malacological survey in city parks in Belo Horizonte, Minas Gerais, Brasil] / Levantamento malacológico em parques urbanos de Belo Horizonte, Minas Gerais, Brasil.

The Greater Metropolitan Area of Belo Horizonte currently contains 18 city parks (also known as "ecological parks") with various bodies of water (lakes, springs, streams, etc). Initial research in 17 of these parks showed the occurrence of intermediate mollusk hosts for Schistosoma mansoni in at least 4. Monthly captures done from August 1994 to February 1996 showed the following results for these planorbids: Julien Rien Park: 1,145 specimens of Biomphalaria glabrata (2 to 13 mm); Betânia Park: 149 specimens of B. glabrata (4 to 13 mm); Santa Lúcia Park: 2,431 specimens of B. straminea (3 to 9 mm); and Lagoa do Nado Park: 3 specimens of B. tenagophila (3 to 10 mm). Visits to the parks will continue, and after a diagnosis of each park's situation, control and/or eradication measures suitable for each one will be proposed to the municipal authorities.