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Query: UMLS:C0015672 (fatigue)
 51,768 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The original central fatigue hypothesis suggested that an exercise-induced increase in extracellular serotonin concentrations in several brain regions contributed to the development of fatigue during prolonged exercise. Serotonin has been linked to fatigue because of its well known effects on sleep, lethargy and drowsiness and loss of motivation. Several nutritional and pharmacological studies have attempted to manipulate central serotonergic activity during exercise, but this work has yet to provide robust evidence for a significant role of serotonin in the fatigue process. However, it is important to note that brain function is not determined by a single neurotransmitter system and the interaction between brain serotonin and dopamine during prolonged exercise has also been explored as having a regulative role in the development of fatigue. This revised central fatigue hypothesis suggests that an increase in central ratio of serotonin to dopamine is associated with feelings of tiredness and lethargy, accelerating the onset of fatigue, whereas a low ratio favours improved performance through the maintenance of motivation and arousal. Convincing evidence for a role of dopamine in the development of fatigue comes from work investigating the physiological responses to amphetamine use, but other strategies to manipulate central catecholamines have yet to influence exercise capacity during exercise in temperate conditions. Recent findings have, however, provided support for a significant role of dopamine and noradrenaline (norepinephrine) in performance during exercise in the heat. As serotonergic and catecholaminergic projections innervate areas of the hypothalamus, the thermoregulatory centre, a change in the activity of these neurons may be expected to contribute to the control of body temperature whilst at rest and during exercise. Fatigue during prolonged exercise clearly is influenced by a complex interaction between peripheral and central factors.
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PMID:Central fatigue: the serotonin hypothesis and beyond. 1700 50

The aim of the present study was to investigate the relationships between heart rate variability (HRV) changes and both training variations and performances in elite swimmers. A secondary purpose was to measure catecholamine urinary excretion in elite swimmers to validate the HRV indices of sympathetic activity during training. Thirteen swimmers (4 females and 9 males) were tested before and after 4 weeks of intense training (IT) and 3 weeks of reduced training (RT). At the end of each period, the swimmers participated in an official competition of their best event. Individual performances were expressed as percentage of the previous season's best performance. Spectral analysis was used to investigate RR interval variability. HRV indices failed to show any significant changes between the study periods (p>0.05). Pre-IT HF was correlated with performance (r=0.45; p=0.05) and HFnu (r=0.59; p<0.05) during RT. On the other hand, once RT was completed, HFnu was correlated positively to performance (r=0.81; p<0.01) and negatively to fatigue (r=- 0.63; p<0.03). Conversely, the indices of sympathetic activity, i.e., LFnu and LF/HF ratio were inversely related to performance (both r=- 0.81; p<0.01); total fatigue score was correlated to the changes in HFnu (r=- 0.63; p<0.03) and in the LF/HF ratio (r=0.58; p<0.05). Changes in the adrenaline/noradrenaline ratio over the follow-up period were related to the changes in the LF/HF ratio (r=0.45; p<0.03). In highly trained swimmers coping well with a training program, including 4 weeks of IT followed by 3 weeks of RT, HRV indices were unaltered. On the other hand, after the 3 weeks of RT, HFnu was positively related to performance and inversely related to the fatigue score. Thus, elevated initial HF levels could be important in the parasympathetic activity increases during taper and, hence, in swimming performance improvement.
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PMID:Heart rate variability, training variation and performance in elite swimmers. 1711 20

Diabetics develop numerous chronic associated diseases, among them sensory polyneuropathy. Diabetic polyneuropathy (DPN) often causes pain of various kinds, degree and duration. There are many pharmacological approaches: antidepressants are also important. Duloxetine is a recently approved dual action serotonin and noradrenaline re-uptake inhibitor that in its analgesic efficacy is comparable to established drugs. Duloxetine, in a dosage of 60 mg x 1 or x 2 daily, significantly reduces, from the first week of administration, the pain of DPN, when compared with a placebo. The most commonly observed side effects have been nausea, sleepiness, constipation and fatigue. On average duloxetine has not shown any clinically relevant increase in blood pressure, pulse rate and weight. It thus offers a new option as part of the treatment of pain caused by DPN. The various drugs should be considered individually in any treatment algorithm, also taking into account their side effects. Psychotherapeutic methods serve to support the overcoming of pain.
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PMID:[Duloxetine, a new therapeutic option for diabetic peripheral neuropathic pain]. 1713 88

Bupropion, a noradrenaline and dopamine re-uptake inhibitor, has long been indicated for the treatment of depression. Recent studies have demonstrated additional benefits in depression, including: prevention of the recurrence of seasonal affective disorder in depressive subtypes with decreased energy, pleasure and interest; in major depression with concomitant anxiety; in elderly depressed patients; for non-response to initial serotonin re-uptake inhibitor therapy or augmentation of partial efficacy with serotonin re-uptake inhibitors; and in bipolar depression. Efficacy in other conditions has also been shown in studies of attention deficit hyperactivity disorder, nicotine dependence, obesity and hypoactive sexual desire disorder. Thus, bupropion has proven effective across a broad spectrum of depressive conditions, subtypes and comorbidities.
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PMID:Extended-release bupropion: an antidepressant with a broad spectrum of therapeutic activity? 1730 40

Fatigue without coincident depression may accompany many neurological disorders, including multiple sclerosis, Parkinson's disease, motor neuron disease, stroke and post-polio syndrome, and is frequently reported by patients as a predominant complaint. The pathophysiology of fatigue is unknown. The role of various mechanisms has been suggested, including the effect of proinflammatory cytokines (TNF-alpha, IL-1beta and IL-6) on glutaminergic transmission, hypothalamo-pituitary-adrenal (HPA) axis dysfunction, disturbances of astroglia metabolism and decreased levels of the neurotransmitters noradrenaline and serotonin. The diagnosis of fatigue syndrome is based on exclusion of depression and additional organic conditions (anaemia, cardiovascular disorders, kidney diseases or hypothyroidism). The treatment of fatigue syndrome is complex. Physical activity, rehabilitation, psychotherapy and avoidance of factors which may increase fatigue, such as fever, anxiety, depression, pain, sleep disturbances, as well as some drugs like opioids and benzodiazepines, are important. Pharmacological treatment leads to slight improvement. Amantadine, modafinil and pemoline are administered to such patients.
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PMID:[Fatigue syndrome in chronic neurological disorders]. 1787 43

A 77-year-old woman who was treated for malignant melanoma was incidentally found to have a bladder tumor on a screening computed tomography (CT). On CT and magnetic resonance imaging (MRI), the tumor was detected as a well-enhanced tumor (4 x 5 cm at horizontal plane) on the left side of the bladder wall. Cystoscopy revealed a small non-papillary pedunculated tumor on the posterior wall and a submucosal tumor on the left side of the wall. We performed transurethral resection of the tumor on the posterior wall and biopsy of the tumor on the left side wall. The pathological diagnosis was paraganglioma of the urinary bladder. Serum and urine levels of noradrenaline and dopamine were elevated. 123I-metaiodobenzylguanidine (MIBG) scintigraphy showed a significant uptake on the left side of the bladder. Blood pressure was normal at rest but elevated after micturition. No pelvic lymph node swelling or distant metastasis was detected. We performed partial cystectomy for the tumor on the left side wall. After operation, serum catecholamine level was normalized and post-voiding fatigue that was present before operation disappeared. Six months after operation, a followup CT revealed a small well-enhanced tumor on the anterior wall of the bladder. Her serum noradrenaline level was slightly elevated. However, she was normotensive and had no symptoms. Therefore, a careful follow-up continued for 2 years there after has revealed no increase in tumor size and no symptoms.
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PMID:[Multiple paraganglioma of the urinary bladder]. 1801 87

The clinical focus of rheumatologists on the widespread pain and numerous tender points in specific anatomic regions in their patients who show no evidence for disease pathology has lead to the characterization of such peripheral symptoms as a specific disorder of the musculoskeletal system, now commonly known as fibromyalgia. This rheumatologic diagnostic entity has resulted in relative inattention to an understanding of their patients' common complaints of unrefreshing sleep, chronic fatigue and psychological distress. Experimental evidence from humans and animal studies indicate that there is an inter-relationship of disturbances in the physiology of the sleeping-waking brain with the widespread musculoskeletal pain, chronic fatigue, and psychological distress in patients with hitherto unexplained pain/fatigue illnesses, e.g., fibromyalgia and chronic fatigue syndromes. The emerging knowledge of the dysfunction of the nervous system in such patients has lead to the study of novel medications that affect neurotransmitter functions, e.g., pregabalin, serotonin/noradrenaline compounds and sodium oxybate that are shown to improve many of the symptoms of such patients.
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PMID:The significance of the sleeping-waking brain for the understanding of widespread musculoskeletal pain and fatigue in fibromyalgia syndrome and allied syndromes. 1845 36

This review examines the pharmacology of stimulants prohibited by the World Anti-Doping Agency (WADA). Stimulants that increase alertness/reduce fatigue or activate the cardiovascular system can include drugs like ephedrine available in many over-the-counter medicines. Others such as amphetamines, cocaine and hallucinogenic drugs, available on prescription or illegally, can modify mood. A total of 62 stimulants (61 chemical entities) are listed in the WADA List, prohibited in competition. Athletes may have stimulants in their body for one of three main reasons: inadvertent consumption in a propriety medicine; deliberate consumption for misuse as a recreational drug and deliberate consumption to enhance performance. The majority of stimulants on the list act on the monoaminergic systems: adrenergic (sympathetic, transmitter noradrenaline), dopaminergic (transmitter dopamine) and serotonergic (transmitter serotonin, 5-HT). Sympathomimetic describes agents, which mimic sympathetic responses, and dopaminomimetic and serotoninomimetic can be used to describe actions on the dopamine and serotonin systems. However, many agents act to mimic more than one of these monoamines, so that a collective term of monoaminomimetic may be useful. Monoaminomimietic actions of stimulants can include blockade of re-uptake of neurotransmitter, indirect release of neurotransmitter, direct activation of monoaminergic receptors. Many of the stimulants are amphetamines or amphetamine derivatives, including agents with abuse potential as recreational drugs. A number of agents are metabolized to amphetamine or metamphetamine. In addition to the monoaminomimetic agents, a small number of agents with different modes of action are on the list. A number of commonly used stimulants are not considered as Prohibited Substances.
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PMID:Pharmacology of stimulants prohibited by the World Anti-Doping Agency (WADA). 1850 Mar 82

It is clear that the cause of fatigue is complex, influenced by both events occurring in the periphery and the central nervous system (CNS). It has been suggested that exercise-induced changes in serotonin (5-HT), dopamine (DA), and noradrenaline (NA) concentrations contribute to the onset of fatigue during prolonged exercise. Serotonin has been linked to fatigue because of its documented role in sleep, feelings of lethargy and drowsiness, and loss of motivation, whereas increased DA and NA neurotransmission favors feelings of motivation, arousal, and reward. 5-HT has been shown to increase during acute exercise in running rats and to remain high at the point of fatigue. DA release is also elevated during exercise but appears to fall at exhaustion, a response that may be important in the fatigue process. The rates of 5-HT and DA/NA synthesis largely depend on the peripheral availability of the amino acids tryptophan (TRP) and tyrosine (TYR), with increased brain delivery increasing serotonergic and DA/NA activity, respectively. TRP, TYR, and the branched-chained amino acids (BCAAs) use the same transporter to pass through the blood-brain barrier, meaning that the plasma concentration ratio of these amino acids is thought to be a very important marker of neurotransmitter synthesis. Pharmacological manipulation of these neurotransmitter systems has provided support for an important role of the CNS in the development of fatigue. Work conducted over the last 20 y has focused on the possibility that manipulation of neurotransmitter precursors may delay the onset of fatigue. Although there is evidence that BCAA (to limit 5-HT synthesis) and TYR (to elevate brain DA/NA) ingestion can influence perceived exertion and some measures of mental performance, the results of several apparently well-controlled laboratory studies have yet to demonstrate a clear positive effect on exercise capacity or performance. There is good evidence that brain neurotransmitters can play a role in the development of fatigue during prolonged exercise, but nutritional manipulation of these systems through the provision of amino acids has proven largely unsuccessful.
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PMID:Amino acids and the brain: do they play a role in "central fatigue"? 1857 73

Bonito extract (BE) has been shown to improve various fatigue-related symptoms. The possibility that the improvement of blood flow contributes to the improvement of fatigue-related symptoms has been reported. However, even though BE has been found to increase peripheral blood flow in humans, an understanding of its mechanisms has remained elusive. The purpose of the present study is to construct an animal model system with which the blood flow-increasing effects of BE can be examined. Using mice loaded with crowding stress, an attempt was made to reproduce the increases in peripheral blood flow observed in humans after a single administration of BE. In this study, the crowded-condition mice (20 mice/cage) showed significantly increased catecholamine levels (noradrenaline, adrenaline, and dopamine) in their circulating blood and a decreased rate of skin blood perfusion in comparison with the normal-condition mice (6 mice/cage). The rate of skin blood perfusion was significantly increased by BE in the crowded-condition mice in comparison with the controls, but not influenced by BE in the normal-condition mice. This suggests that BE expands the vascular diameter by affecting the constriction of vessels induced by catecholamines.
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PMID:Ingestion of bonito extract ameliorates peripheral blood flow in mice loaded from over crowding stress. 1942 Jul 37


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