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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 52 (1989), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Patients with normal pressure hydrocephalus who had three lumbar punctures during 1 week ingested either water, a protein breakfast, or a carbohydrate breakfast 2.5 h before each of the lumbar punctures. The CSF was analyzed for biogenic amine precursors and metabolites. The protein meal raised CSF tyrosine levels, a finding consistent with animal data, but did not alter those of tryptophan or any of the biogenic amine metabolites. The carbohydrate meal increased CSF 3-methyoxy-4-hydroxyphenylethylene glycol, an unexplained finding. The carbohydrate meal did not affect CSF tryptophan, tyrosine, 5-hydroxyindoleacetic acid, or homovanillic acid. Our results support the idea that in humans protein or carbohydrate meals do not alter plasma amino acid levels sufficiently to cause appreciable changes in CNS tryptophan levels or 5-hydroxytryptamine synthesis.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Tryptophan, 5-hydroxyindoleacetic acid (5HIAA), and indoleacetic acid (IAA) were measured in rat cerebrospinal fluid (CSF) using high-performance liquid chromatography with fluorometric detection in order to study brain indoleamine metabolism. Previously we have shown that IAA in CSF is derived from tryptamine in the CNS. In this study our results indicated that the synthesis of both 5-hydroxytryptamine (5HT) and tryptamine varied with changes in brain tryptophan. After a tryptophan load, tryptamine synthesis increased much more than 5HT synthesis; under these circumstances, it can be of the same order of magnitude as 5HT synthesis. Studies with treatments that cause release of 5HT (reserpine and cold stress) indicated that tryptamine is not released with 5HT and is probably not stored in vesicles. Use of selective monoamine oxidase inhibitors suggested that results obtained in vitvo concerning the substrates for monoamine oxidase A and B apply in vivo. Thus, 5HT was acted on preferentially by the A enzyme, and tryptamine by the B enzyme. Measurement of IAA in brain, CSF, and plasma before and after probenecid indicated that there are active transport systems moving IAA from CSF and brain to blood, and from brain to CSF. Our data suggest that measurements of CSF IAA are a simple and convenient way of studying CNS tryptamine metabolism and should be applied clinically.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 42 (1984), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Biogenic amine precursors and metabolites were measured in cisternal cerebrospinal fluid from 83 female and 55 male vervet monkeys. The results indicate that mean rates of 5-hydroxytryptamine, dopamine, and noradrenaline metabolism in the brain are higher in females than in males. They also suggest that under physiological circumstances tryptophan availability is involved in the control of brain 5-hydroxytryptamine synthesis while tyrosine availability is involved in control of both dopamine and noradrenaline metabolism. The similarities seen between our results on vervets and those seen with human cerebrospinal fluid suggest that the vervet is a useful primate to study.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 78 (2001), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: α-Methyl-l-tryptophan (α-MTrp) is an artificial amino acid and an analog of tryptophan (Trp), the precursor of the neurotransmitter serotonin (5-HT). In this article we have summarized available data, which suggest that the measurement of the unidirectional uptake of α-MTrp and its conversion to 5-HT synthesis rates is a valid approach for the determination of brain 5-HT synthesis rates. The main feature on which the model is based is the trapping of labeled α-MTrp in brain tissue. An overview of opposing opinions, which suggest that there is a need for a metabolic conversion of tracer, is also presented and discussed critically. As with all biological modeling there is likely to be room for improvements of the proposed biological model. In addition, there are a limited number of clearly defined circumstances in which the method is confounded by the metabolism of labeled α-MTrp via the kynurenine pathway. Nonetheless, a significant body of evidence suggests that labeled α-MTrp is a useful tracer to study brain 5-HT synthesis in most circumstances. Calculation of 5-HT synthesis rates depends on the plasma-free tryptophan concentration, which, according to the balance of arguments in the literature, is a more appropriate parameter than the total-plasma tryptophan. The method, as proposed by us, can be used in conjunction with autoradiographic measurements in laboratory animals, and with positron emission tomography in large animals and humans. We review studies in animals looking at the normal control of 5-HT synthesis and the way in which it is altered by drugs, as well as initial studies investigating healthy humans and patients with neuropsychiatric disorders.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 34 (1980), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Using a new high performance liquid chromatographic method we have measured tryptophan, 5-hydroxyindoleacetic acid (5HIAA), indoleacetic acid (IAA), and indolepropionic acid (IPA) in rat and human CSF. Experiments on rats indicate that IPA in CSF is not derived from the CNS but from bacterial metabolism in the intestine. However, IAA in CSF is derived from CNS tryptamine metabolism. Some tryptamine that is formed peripherally diffuses across the blood-brain barrier and augments the tryptamine formed within the CNS. We have concluded from our data that (i) measurements on CSF are a useful way of studying trace amine metabolism in human CNS, but it is essential to establish the anatomical and metabolic origin of any metabolite found in the CSF; and (ii) tryptamine metabolism is more important in man than in the rat.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Psychopharmacology 98 (1989), S. 508-511 
    ISSN: 1432-2072
    Keywords: Tryptophan ; 5-Hydroxytryptamine ; Humans ; Vervet monkeys
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We studied the degree of plasma tryptophan depletion produced by giving normal human males different amounts of a tryptophan-free (T-) amino acid mixture. From the results of this and other studies we concluded that the maximum degree of tryptophan depletion can be produced by a 31.5 g mixture of seven essential amino acids. Administration of a T−amino acid mixture to vervet monkeys lowered tryptophan and 5-hydroxyindoleacetic acid in the cerebrospinal fluid. Levels of tyrosine and the catecholamine metabolites were unchanged. These data support the idea that the effects of T−mixture on mental function in humans which have been reported previously are due to a decrease in 5-hydroxytryptamine.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1432-2072
    Keywords: Tryptophan ; Tyrosine ; Phenylalanine ; Motor activity ; Biogenic amines ; Antidepressant
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Behaviour was observed in mice given L-tryptophan, L-tyrosine or L-phenylalanine and then placed either in an open field or in water in a narrow cylinder. Animals placed in water (swim test) soon assume a characteristic immobile posture. Most antidepressants, including pharmacologically atypical ones, decrease immobility in the swim test while many decrease or do not affect activity in the open field test. Tryptophan increased immobility in the swim test, but did not affect open field activity and thus did not exhibit the normal profile of activity for an antidepressant. Tyrosine decreased immobility in the swim test and markedly increased activity in the open field test, an action similar to the psychostimulants amphetamine and caffeine. Phenylalanine decreased immobility in the swim test, but did not affect open field activity. Thus, its behavioural effects are similar to those of an antidepressant. As expected, tryptophan increased brain tryptophan and serotonin in a dose-related fashion. Tyrosine did not alter dopamine or noradrenaline levels, while phenylalanine lowered dopamine, noradrenaline and serotonin. These biochemical data do not fully explain the behavioural results.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Psychopharmacology 87 (1985), S. 173-177 
    ISSN: 1432-2072
    Keywords: Tryptophan ; 5-Hydroxytryptamine ; Depression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Normal male human subjects ingested amino acid mixtures which were tryptophan-free, balanced or contained excess tryptophan. The tryptophan-free mixture causes a marked depletion of plasma tryptophan by 5 h. At this time the subjects in the tryptophan-free group had significantly elevated scores on the depression scale of the Multiple Affect Adjective Checklist. The tryptophan-free group also performed worse than the other two groups in a proofreading task carried out while listening to a tape with themes of hopelessness and helplessness (dysphoric distractor). Cognitive theories of depression predict greater distractability of depressed individuals by dysphoric themes. Thus, both measures indicate a rapid mood lowering effect of tryptophan depletion in normal males. This effect is probably mediated by a lowering of brain 5-hydroxytryptamine. Although the mood-lowering effect was not as great as that seen in depressed patients, our results suggest that low brain 5HT might be one factor precipitating depression in some patients.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1432-2072
    Keywords: Ethanol ; Aggression ; Tryptophan ; Serotonin ; Tryptophan Depletion ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Normal males received amino acid mixtures designed to raise or lower tryptophan availability, and thus to raise or lower brain serotonin synthesis. They also received alcoholic or non-alcoholic drinks. The subjects were tested in the Taylor Competitive Reaction Time Task in which they competed against a (non-existent) partner in a reaction time task. The magnitude of electric shocks that the subjects were willing to give to their bogus partner was used as a measure of aggression. Lowered tryptophan levels and ingestion of alcohol were associated with increased aggression. Our data support the idea that low serotonin levels may be involved in the etiology of aggression. They suggest that subjects with low brain serotonin levels may be particularly susceptible to alcohol-induced violence.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1432-2072
    Keywords: Key words Tyrosine ; Dopamine ; Noradrenaline ; Cerebrospinal fluid ; Cercopithecus aethiops ; Alcohol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  An amino acid mixture devoid of tryptophan, given orally, was previously shown to reduce cerebrospinal fluid levels of tryptophan and 5-hydroxyindoleacetic acid in vervet monkeys, as compared to a control mixture containing all essential amino acids. In the present study, we tested the possibility that a similar amino acid mixture containing tryptophan, but devoid of phenylalanine and tyrosine (the amino acid precursors of catecholamine neurotransmitters), would influence dopamine and noradrenaline metabolism. Five hours after the administration of this mixture to vervet monkeys, cerebrospinal fluid levels of homovanillic acid and 3-methoxy-4-hydroxyphenylethylene glycol were reduced by 27.4% and 26.9%, respectively. Both effects were statistically significant. Plasma tyrosine (-30%) and the ratio of tyrosine to the sum of other large neutral amino acids (ΣLNAA) were also significantly reduced. The behavioral efficacy of phenylalanine/tyrosine depletion was compared with that of tryptophan depletion in a primate model of voluntary alcohol consumption. All three drinks lowered alcohol consumption, but the effects of the tryptophan-deficient amino acid mixture were not different from those of the balanced amino acid control. The phenylalanine/tyrosine-deficient drink differentially lowered alcohol consumption, consistent with other data in this species and elsewhere implicating dopamine in the rewarding effects of alcohol.
    Type of Medium: Electronic Resource
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