The Parkinson fatigue scale, 2005
Physical exercise-induced fatigue: the role of serotonergic and dopaminergic systems. 2017
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.
Central fatigue induced by losartan involves brain serotonin and dopamine content. 2010
To investigate the influence of angiotensin II (Ang II) AT1 receptors blockade on central fatigue induced by brain content of serotonin (5-HT) and dopamine (DA) during exercise.
Losartan (Los) was intracerebroventricularly injected in rats before running until fatigue (n = 6 per group). At fatigue, brains were quickly removed for measurement of 5-HT, 5-hydroxyindoleacetic acid (5-HIAA), DA, and 3,4-dihydroxyphenylacetic acid by high-pressure liquid chromatography in the preoptic area, hypothalamus, hippocampus, and frontal cortex.
Intracerebroventricular injection of Los increased 5-HT content in the preoptic area and hypothalamus. Such results correlated positively with body heating rate and inversely with time to fatigue. On the other hand, time to fatigue was directly correlated with the diminished concentration of 5-HT in the hippocampus of Los rats. Although the levels of DA were not affected by Los treatment during exercise in any of the brain areas studied, a higher 5-HT/DA ratio was seen in the hypothalamus of Los animals. This higher hypothalamic 5-HT/DA ratio correlated positively with body heating rate and negatively with time to fatigue.
Our results show that central fatigue due to hyperthermia and increased body heating rate induced by central Ang II AT1 receptor blockade in exercising rats is related with higher 5-HT content in the preoptic area and hypothalamus as well as with decreased levels of this neurotransmitter in the hippocampus. Furthermore, the interaction between 5-HT and DA within the hypothalamus seems to contribute to hyperthermia and premature central fatigue after angiotensinergic inhibition.
Fatigue and levodopa
levodopa and thyroid function
Sinemet and thyroid function in Parkinson disease. 1979
Patients on chronic carbidopa-levodopa (Sinemet) therapy underwent thyroid function testing that included measurement of serum thyroxine (T4), triiodothyronine (t3), thyrotropin (TSH), T3 uptake (T3U), free T4 index (FT4I), and free T3 index (FT3I). The subjects were studied both in a random sampling and in a controlled manner, fasting and 2 hours after receiving the drug. All subjects were euthyroid by testing, and there was no significant difference in thyroid hormone levels of patients and controls or in fasting values and values 2 hours after the drug. However, there was a small but significant reduction in serum TSH levels after Sinemet. Therapeutic doses of Sinemet have no significant effect on thyroid function in euthyroid patients with Parkinson disease.
L-DOPA decreases PRL (not always)