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

Amphetamine, caffeine, sydnocarb, meclofenoxate, adapromine, midantan, and nomifensine were studied for their effects on bioelectrical activity and Fourier EEG power spectra of the sensomotor cortex, dorsal hippocamp and lateral hypothalamus of freely behaving awake rats. The drop in the absolute power of all frequency ranges with the enhanced power of fast beta 1,2-ranges was common to the action of psychostimulants. In addition to the common properties, specific features of their action were revealed. Amphetamine, meclofenoxate, and nomifensine were found to increase the amplitude of the dominant peak in the theta-range and amphetamine shifts the frequency of the dominant peak to the region of faster ranges. The agents-induced electrophysiological changes correspond to the varying degrees of activation of the central nervous system, causing the optimization of behavioral functions, abolition of fatigue and drowsiness and enhancing physical and mental working capacity.
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PMID:[Comparative quantitative pharmacological-EEG analysis of the effects of psychostimulants]. 762

Caffeine is widely consumed in beverages to obtain mild CNS stimulant effects. Long term use produces tolerance to some of the pharmacological effects. Withdrawal of caffeine, even from moderate intake levels, can produce symptoms such as headache, fatigue and anxiety. Caffeine is used therapeutically in combination with ergotamine for migraine headaches and in combination with nonsteroidal anti-inflammatory drugs in analgesic formulations. Caffeine alone is used as a somnolytic, to treat various headache conditions, respiratory depression in neonates, postprandial hypotension and obesity, and to enhance seizure duration in electroconvulsive therapy. In some headache and in pain paradigms, caffeine may produce direct adjuvant analgesic properties, while in other headache conditions (perioperative, postdural puncture) caffeine may be effective by alleviating a manifestation of caffeine withdrawal. Other uses, such as to promote wakefulness, for respiratory stimulation and seizure prolongation, rely on central stimulant properties of caffeine. Effects of caffeine on the vasculature may contribute to the relief of some headaches and in postprandial hypotension. Blockade of methylxanthine-sensitive adenosine receptors is the currently accepted mechanism of action of caffeine.
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PMID:Pharmacological rationale for the clinical use of caffeine. 770 15

1. Mechanically skinned fast-twitch (FT) and slow-twitch (ST) muscle fibres of the rat were used to investigate the effects of fatigue-like changes in creatine phosphate (CP) and inorganic phosphate (P(i)) concentration on Ca(2+)-activation properties of the myofilaments as well as Ca2+ movements into and out of the sarcoplasmic reticulum (SR). 2. Decreasing CP from 50 mM to zero in FT fibres increased maximum Ca(2+)-activated tension (Tmax) by 16 +/- 2% and shifted the mid-point of the tension-pCa relation (pCa50) to the left by 0.28 +/- 0.03 pCa units. In ST fibres, a decrease of CP from 25 mM to zero increased Tmax by 9 +/- 1% and increased the pCa50 by 0.16 +/- 0.01 pCa units. The effect of CP on Tmax was suppressed in both fibre types by prior treatment with 0.3 mM FDNB (1-fluoro-2,4-dinitrobenzene), suggesting that these effects may occur via changes in creatine kinase activity. 3. Increases of P(i) in the range 0-50 mM reduced the pCa50 and Tmax in both fibre types. These effects were more pronounced in ST fibres than in FT fibres in absolute terms. However, normalization of the results to resting P(i) levels appropriate to both fibre types (1 mM for FT and 5 mM for ST fibres) revealed similar decreases in Tmax (approximately 39% at 25 mM P(i) and approximately 48% at 50 mM P(i)) and pCa50 (0.25 pCa units at 25-50 mM P(i)). The depressant action of P(i) on both parameters was considerably reduced when the rise in P(i) was accompanied by an equivalent reduction in [CP]. 4. Tension development in the presence of complex, fatigue-like milieu changes (40 mM P(i) for FT; 20 mM P(i) for ST) was decreased by 35-40% at a constant myoplasmic [Ca2+] of 6 microM in both fibre types. 5. SR Ca2+ loading at a myoplasmic [Ca2+] of 100 nM was found to increase abruptly when the [P(i)] during loading was increased to near 9 mM. At a myoplasmic [Ca2+] of 300 nM, the threshold P(i) for this effect dropped to approximately 3 mM. 6. Tension responses evoked by caffeine in the absence of P(i) were smaller and slower to peak if fibres were exposed to P(i) in a restricted myoplasmic Ca2+ pool after SR Ca2+ loading. This indicated that myoplasmic P(i) can decrease and prolong the rate of Ca2+ release from the SR.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Effects of creatine phosphate and P(i) on Ca2+ movements and tension development in rat skinned skeletal muscle fibres. 773 Sep 77

In experiment 1 eight male and eight female subjects were randomly assigned to either a caffeine or a placebo condition. Caffeine (150 mg) was given at midnight and at 4 a.m. Oral temperature, subjective ratings of fatigue and mood, and performance in two cognitive tasks (an auditive attention task and a visual coding task) were assessed. Subjective 'drowsiness' and 'tiredness' increased significantly more in subjects given placebo than in subjects given caffeine treatment. The effects of drug treatment in performance and temperature were non-significant. However, the temperature of female subjects increased between midnight and 4 a.m. and the temperature of male subjects decreased during the same period of time. On the other hand, at 5 a.m. female subjects rated themselves as more sleepy, tired and 'disorganized' than the male subjects. In experiment 2 nine female and nine male subjects were assigned randomly to either placebo or caffeine treatment. Caffeine (200 mg) was given at 5 a.m. Oral temperature, subjective ratings of fatigue and mood, and level of performance in three cognitive tasks (the same as above plus Raven's progressive matrices) were assessed. Moreover, the subjects rated the effort of performing each task. The effects of drug treatment in level of performance were non-significant. However, the subjective effort of performing the auditive attention task increased significantly in subjects given placebo treatment, suggesting a compensatory arousal mechanism (Broadbent 1971). The effect of gender on temperature was non-significant. There was a significant interaction between gender and treatment in respect of subjective effort of performing the matrices task. In men caffeine decreased subjective effort and in women subjective effort was increased by caffeine. Experiment 3 was set up to investigate the hypothesis that negative effects of caffeine in women, observed in experiment 2, were due to over-optimal ('vigilance-related') arousal for the visual coding and matrices tasks. Ten female and eight male non-sleep deprived subjects were given 200 mg caffeine or placebos at 3 p.m. and tested at 4 p.m. Experiment 3 was not found to support the over-optimal 'vigilance-related-arousal' hypothesis. Effects of caffeine in performance and effort were non-significant in experiment 3. Combining data from experiments 2 and 3 gave a significant three-way interaction between caffeine, time for experiment and rule complexity in the visual coding task. When there was a complex rule, caffeine was found to have a positive effect in experiment 3 and a negative effect in experiment 2.
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PMID:Mental effects of caffeine in fatigued and non-fatigued female and male subjects. 773 3

The effects of caffeine on different information processing stages were examined by using choice reaction time tasks. Independent variables were stimulus degradation, stimulus-response compatibility, time-uncertainty, state of the subject, and caffeine treatment. The task variables were assumed to affect the following processing stages; encoding, response selection and motor preparation, respectively. A 200 mg dose at the beginning of the experiment and a maintenance dose of 50 mg caffeine or lactose half-way through the session were administered to well rested and fatigued subjects, double-blind and deceptively. Behavioural measurements, event-related potentials (ERPs) and mood questionnaires were used to assess caffeine effects. The data showed that caffeine shortened reaction time. This effect showed an interaction with stimulus degradation and time uncertainty. In addition, ERP results supported the view that caffeine increases cortical arousal and perceptual sensitivity. Stimulating effects of caffeine were mainly located at input and output stages of the information processing system. Central processes were unaffected by caffeine. Fatigued subjects showed larger improvements in performance after caffeine than well-rested subjects. The results also indicated that caffeine effects were not stimulating in all subjects: 6 out of 30 subjects did not show arousing effects of caffeine.
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PMID:Influence of caffeine on information processing stages in well rested and fatigued subjects. 786 53

Food and symptom diaries were used to identify problem foods for each of 164 patients with chronic medical problems such as headache, fatigue, congestion, abdominal pain, and sinus problems. A statistical analysis related the total load of 90 biologic families, as well as caffeine, alcohol, and lactose, to changes in symptom intensity during a 2-week diary. The results helped 75% of the patients when used as a guide for elimination diets. Open challenges confirmed 47% of the identified food components. This study required a database and software to estimate recipe components for an average of 243 foods per patient. The analysis of each patient's diary produces a main report that lists suspect food components for each symptom. The report lists components in decreasing order of statistical confidence and gives lag times between food ingestion and symptom change. This report also shows that initial direction of the symptom change as a direct or masking effect. Foods that appear "safe" or unrelated to the symptoms are also listed. A second report lists the patient's food sources for each of the suspected food components. The report shows the percentage contribution of source foods and is useful for patient education and the design of elimination diets.
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PMID:Identification of problem foods using food and symptom diaries. 787 Apr 42

Psychomotor stimulant drugs such as caffeine, nicotine, amphetamine and cocaine, have been shown to improve vigilance in man under conditions of fatigue. Nicotine has also been shown to improve performance in some cognitive tests in patients with Alzheimer's disease. In rodents these drugs increase activity which may confound "performance enhancing effects" in rodent models. However, improvements have been found in a number of tests that do not seem to be directly dependent upon an enhancement of locomotor activation. In one example, Evenden and Robbins (1985) reported consistent improvements in a visual tracking test following amphetamine. The present study was undertaken to determine whether these performance enhancing effects of amphetamine could also be obtained with cocaine and apomorphine, which both have psychomotor stimulant effects through their actions as, respectively, indirect and direct dopamine agonists, and by caffeine and nicotine, which do not have a direct dopaminergic mechanism of action. The results of the study indicate that all five drugs improved tracking performance at one or more doses. The most consistent effects were obtained with amphetamine which, like cocaine and nicotine, improved tracking at a dose which did not produce other changes in behaviour. Taking into account previous studies (Evenden and Robbins 1983, 1985), these results were interpreted as indicating that psychomotor stimulant drugs produce a general activation of behaviour. At all but the highest doses of such drugs, the form of behaviour that is observed depends upon the environment.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Caffeine and nicotine improve visual tracking by rats: a comparison with amphetamine, cocaine and apomorphine. 787 Aug 79

This study assessed the ability of high doses of caffeine to reverse changes in alertness and mood produced by prolonged sleep deprivation. Fifty healthy, nonsmoking males between the ages of 18 and 32 served as volunteers. Following 49 h without sleep, caffeine (0, 150, 300, or 600 mg/70 kg, PO) was administered in a double-blind fashion. Measures of alertness were obtained with sleep onset tests, the Stanford Sleepiness Scale (SSS), and Visual Analog Scales (VAS). Sleep deprivation decreased onset to sleep from a rested average of 19.9 min to 7 min. Following the highest dose of caffeine tested, sleep onset averaged just over 10 min; sleep onset for the placebo group averaged 5 min. Scores on the SSS increased from a rested mean of 1.6-4.8 after sleep deprivation. Caffeine reduced this score to near rested values. Caffeine reversed sleep deprivation-induced changes in three subscales of the POMS (vigor, fatigue, and confusion) and produced values close to fully rested conditions on several VAS. Serum caffeine concentrations peaked 90 min after ingestion and remained elevated for 12 h. This study showed that caffeine was able to produce significant alerting and long-lasting beneficial mood effects in individuals deprived of sleep for 48 h.
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PMID:Caffeine reversal of sleep deprivation effects on alertness and mood. 787 Oct 42

Healthy sleeping habits is a complex balance between behaviour, environment and circadian rhythm. The quality of sleep can be improved by behaviour, e.g. eating tryptophan and carbohydrate rich foods, physical exercise in the afternoon or a cold shower just before going to bed. Total sleep time is maximal in thermoneutrality and decreases above and below the thermoneutrality zone. Thermoneutrality is reached for an environmental temperature of 30-32 degrees C without night clothing or of 16-19 degrees with a pyjama and at least one sheet. Noise also modifies sleep structure and above 50dB shortens total sleeping time. Although subjects do become subjectively accustomed to noise, vegetative cardiovascular reactivity to environmental noise remains unchanged. The spontaneous circadian awake/sleep cycle is 25 hours, slightly longer than the body temperature cycle, but when subjects are exposed to environmental synchronization, the two cycles coincide. In individuals undergoing temporal isolation, the two rhythms become independent often leading to subjective discomfort and fatigue. Certain factors including age can favour internal desynchronization. Other factors may include social contact, stress due to mental work load, and constant lighting which could lengthen the awake/sleep cycle. Caffeine blocks the receptors of adenosine, and thus its effects of inhibiting neurotransmission. Intake 30 to 60 minutes before sleeping shortens total sleep time and increases the duration of stage 2 and shortens stage 3 and 4. Alcohol may act as a relaxing, sedative agent when consumed just before sleeping but can also lead to night-time awakening due to sympathetic activation which does not return to baseline levels until the blood alcohol levels have returned to 0. Nicotine has a biphasic effect on sleep: at low concentrations, it leads to relaxation and sedation and at high concentrations inhibits sleep. A careful study of sleeping habits is the first step in evaluating complains of insomnia or hypersomnia. Before relying on drugs, treatment should start with attention to the sleep environment and personal habits.
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PMID:[Prevention and treatment of sleep disorders through regulation] of sleeping habits]. 802 26

The effects of caffeine on diaphragmatic contractility and fatigue was investigated in 21 dogs. Diaphragmatic contractility was assessed by measuring transdiaphragmatic pressure (Pdi) during supermaximal stimulation of the phrenic nerves at different frequencies, and Pdi was measured with a pair of balloons. In protocol 1, the effect of caffeine on contractility of non-fatigued diaphragm was studied in 7 dogs. Caffeine infusion increased Pdi significantly at all frequencies of stimulation. In protocol 2, diaphragmatic fatigue was induced by electrophrenic stimulation (30 Hz, duty cycle 1.0, 30 minutes). The recovery profile after fatigue run was observed in 5 dogs. In another group of 9 dogs, caffeine was infused during stable fatigue period and Pdi increased significantly at all frequencies of stimulation after caffeine infusion. The increase in Pdi was not due to changes in cardiac output or lung mechanics (Cdyn and Rtot), neither of which changed significantly after caffeine infusion. We conclude that caffeine improves muscle contractility both in non-fatigued and fatigued diaphragm in dogs.
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PMID:Effects of caffeine on diaphragmatic contractility and fatigue. 803 8


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