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  • Electronic Resource  (16)
  • 1
    Electronic Resource
    Electronic Resource
    Effect of Tryptophan on Extracellular Concentrations of Tryptophan and 5-Hydroxyindoleacetic Acid in the Striatum and Cerebellum (1991)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 56 (1991), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: The effects of l-tryptophan (50 mg/kg i.p.) on extracellular concentrations of tryptophan and the 5-hydroxy-tryptamine (5-HT) metabolite 5-hydroxyindoleacetic acid (5-HIAA) were determined in the rat striatum and cerebellum, regions with rich and poor 5-HT innervation, respectively. Determinations were on perfusates from dialysis probes in the brains of conscious, freely moving rats. The pharmaco-kinetic profiles of dialysate tryptophan after tryptophan load (peak concentration, time to peak concentration, area under curve, and half-life) in the two regions did not differ significantly. The dialysate 5-HIAA concentration in the striatum rose two- to threefold after the administration of tryptophan. Therefore, as 5-HIAA was undetectable in the cerebellum either before or after the administration of tryptophan, the increase of 5-HIAA in the striatum is unlikely to depend appreciably on its production within the cerebral vasculature or outside the brain or on its entering the striatum through a blood-brain barrier damaged by placement of the dialysis probe. Overall, the findings strengthen previous evidence that extracellular 5-HIAA concentrations determined by cerebral dialysis are a valid measure of the metabolism of 5-HT of brain neuronal origin.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1991.tb02052.x
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  • 2
    Electronic Resource
    Electronic Resource
    Effect of Transient Cerebral Ischaemia and Cardiac Arrest on Brain Extracellular Dopamine and Serotonin as Determined by In Vivo Dialysis in the Rat (1990)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 55 (1990), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: The effects of 20-min transient, global, forebrain ischaemia and cardiac arrest on extracellular concentrations of dopamine (DA), serotonin (5-HT), and their respective metabolites, homovanillic acid (HVA) and 5-hydroxyindole-acetic acid (5-HIAA), were measured in vivo by dialysis of rat striatum and hippocampus. During the ischaemic period, striatal DA content increased (250-fold basal concentrations) with parallel but much less marked increases of both striatal and hippocampal 5-HT content (eight- to 10-fold). Baseline values were restored during reperfusion. Subsequent increases of DA and 5-HT levels on cardiac arrest were comparable after both sham operation and ischaemia. Significant decreases of HVA and 5-HIAA levels were observed following ischaemia or cardiac arrest. The differential effects of ischaemia on DA and 5-HT suggest selective alterations in disposition or metabolism of the two transmitters and that dopaminergic neurones may be more vulnerable to ischaemic insults.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1990.tb04581.x
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  • 3
    Electronic Resource
    Electronic Resource
    Changes in Extracellular and Rat Brain Tissue Concentrations of D-β-Hydroxybutyrate After 1, 3-Butanediol Treatment (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 62 (1994), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: 1, 3-Butanediol (BD) treatment was previously shown to produce a dose-related increase of the plasma levels of D-β-hydroxybutyrate (BHB) and to protect brain tissue against hypoxia and ischemia. The purpose of this study was to test whether BD-induced hyperketonemia was associated with changes in brain extracellular and tissue concentrations of BHB. Changes in extracellular levels of BHB were continuously monitored in anesthetized rats before and after intraperitoneal injection of BD (25 mmol/kg), using intracerebral microdialysis coupled to online analysis of BHB in the dialysate. Cortical tissue concentrations of BHB were determined in control and BD- treated rats (25 and 50 mmol/kg, i.p.) after freezing of the brain in situ. Butanediol produced a rapid increase in dialysate levels of BHB, with a linear relationship between dialysate and plasma BHB concentrations (r=0.81, p 〈 0.001). In contrast, and although brain tissue levels of BHB were markedly increased after BD treatment, they were not related to the plasma concentration of BHB. Our results suggest that BHB produced from BD did not accumulate in brain and that BD protects against hypoxia or ischemia by increasing brain BHB availability.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1471-4159.1994.62010223.x
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  • 4
    Electronic Resource
    Electronic Resource
    3,4-Dihydroxyphenylethylamine and 5-Hydroxytryptamine Metabolism in the Rat: Acidic Metabolites in Cisternal Cerebrospinal Fluid Before and After Giving Probenecid (1985)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 45 (1985), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: 3,4-Dihydroxyphenylethylamine (DA, dopamine) and 5-hydroxytryptamine (5-HT) turnover values were determined in freely moving male rats by measuring the rates of accumulation of the acidic metabolites of the above transmitters, i.e., 3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA), and 5-hydroxyindoleacetic acid (5-HIAA) in cisternal cerebrospinal fluid (CSF) samples after probenecid (200 mg/kg i.p.) administration. Determinations on samples before and after acid hydrolysis showed that the latter procedure was necessary for DA turnover determination. Thus whereas total (DOPAC + HVA) increased linearly with time after probenecid, free (DOPAC + HVA) did not. This was because the percentage of DOPAC + HVA in conjugated form increased with time. Determinations on a group of 28 rats during the dark (red light) period showed that cisternal amine metabolite concentrations before probenecid injection did not parallel turnover values. This was probably because individual differences in metabolite egress strongly affect the pre-probenecid values. The poor correlations between CSF tryptophan and 5-HT turnover suggested that differences of brain tryptophan concentration were not major determinants of differences of brain 5-HT metabolism within this group of normal rats. Considering that the rats were of similar weight and that the turnover values were all determined at approximately the same time of day, the three- to fourfold ranges of the turnover values are remarkable. The positive correlation between the DA and 5-HT turnovers of individual rats suggests the existence of common effects on DA and 5-HT turnover in normal rats.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1985.tb04017.x
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  • 5
    Electronic Resource
    Electronic Resource
    Variables Influencing the Effect of a Meal on Brain Tryptophan (1985)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 44 (1985), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Previous work from our laboratory points to plasma free tryptophan being a useful predictor of brain tryptophan concentration in many circumstances. Other work, in particular various studies on the acute effects of food intake, has emphasized the roles of plasma total tryptophan and of plasma large neutral amino acids that compete with tryptophan for transport to the brain. We have now studied associations between the above variables under different dietary conditions. Rats were allowed to feed for restricted periods during a 12-h light-12-h dark cycle. In the first study, rats were given access to a carbohydrate diet for 2 h midway through the light cycle and following an 18-h fast. The resultant rise of brain tryptophan was explicable largely by the associated fall in large neutral amino acids. In a second study, rats were adapted to a regimen whereby they were allowed access to the standard laboratory diet for 4 h during the dark cycle for 3 weeks. A postprandial decrease in brain tryptophan was associated with a fall in free tryptophan and of its ratio to competing amino acids. The brain change could be attributed neither to changes in plasma total tryptophan (which increased) nor to changes of its ratio to the competers (which remained unchanged). Results as a whole are thus consistent with changes of plasma free tryptophan and large neutral amino acid concentrations affecting brain tryptophan concentration under different dietary circumstances. It is suggested that these influences serve to maintain brain tryptophan when dietary supplies are defective.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1985.tb08797.x
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  • 6
    Electronic Resource
    Electronic Resource
    Determination of Brain 5-Hydroxytryptamine Turnover in Freely Moving Rats Using Repeated Sampling of Cerebrospinal Fluid (1983)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 40 (1983), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: A simple technique is described for repeated sampling of cerebrospinal fluid (CSF) from the freely moving rat and its use in the determination of 5-hydroxytryptamine (5-HT) turnover validated. A catheter, constructed from polyethylene tubing (PP10) was implanted via a cranial approach into the cisterna magna and x-ray studies confirmed that the catheter avoided the cerebellum. 5-HT turnover was determined from the rate of rise of 5-hydroxyindoleacetic acid (5-HIAA) in both CSF and brain following an injection of probenecid (200 mg/kg i.p.), Concentrations of 5-HIAA, 5-HT and trypto-phan were determined by high pressure liquid chromatog-raphy. Turnover values for individual rats were obtained using CSF samples. After p-chlorophenylalanine treatment (when brain 5-HT was depleted by 43%) 5-HT turnover values obtained were comparably reduced whether determined from CSF (67%) or brain (74%). Thus differences of rat brain 5-HT turnover are proportionately reflected by CSF measurements. The method for sampling of CSF should be applicable in a wide range of pharmacological and physiological situations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1983.tb11293.x
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  • 7
    Electronic Resource
    Electronic Resource
    Effect of Age on Variables Influencing the Supply of Tryptophan to the Brain (1982)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 39 (1982), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: The relations of plasma concentrations of substances claimed to influence brain tryptophan concentration (total tryptophan, free tryptophan, large neutral amino acids) with the concentrations of tryptophan, 5-hydroxytryptamine (5-HT), and 5-hydroxyindoleacetic acid (5-HIAA) in the forebrain were investigated in rats of different ages (from 8 days to 16 months after birth). In brain, tryptophan fell by 46%, whereas 5-HT rose by 20% between 8 and 40/42 days after birth. Thereafter, the levels of both tryptophan and 5-HT remained essentially constant. Brain 5-HIAA showed a more complex pattern, rising by 63% between 8 and 19 days, falling between 19 and 40/42 days, and then gradually rising until values at 16 months were significantly higher than those at 40/42 days. In plasma, the concentrations of free fatty acids, free and total tryptophan, and large neutral amino acids all decreased between 8 and 19 days and thereafter either remained constant or increased slowly, the exception being total tryptophan values, which showed large increases between 28/30 and 60/70 days. Also, the unidirectional uptake of tryptophan from blood to brain was determined using a carotid artery injection technique. Uptake values obtained using a tracer concentration of tryptophan in the injection solution decreased progressively with age. Kinetic analysis of the data in terms of the Michaelis-Menten equation for carrier-mediated transport indicated significantly lower values for Vmax and KD (a component for nonsaturable transport) in 6-month-old rats as compared to 19-day-old suckling rats, whereas Km values were the same at both ages. Detailed analysis of these results indicated that the age-related changes in brain tryptophan were largely explicable in terms of plasma free tryptophan in association with blood-brain transport characteristics; moderate differences in concentration of amino acids competing for transport were without apparent effect between 19 days and 16 months. The larger differences between 8 and 19 days after birth could be important.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1982.tb12567.x
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  • 8
    Electronic Resource
    Electronic Resource
    ESTIMATION OF THE KINETIC PARAMETERS OF UNIDIRECTIONAL TRANSPORT ACROSS THE BLOOD-BRAIN BARRIER (1979)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 33 (1979), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— The unidirectional transport of metabolic substrates from blood to brain may be defined in terms of Michaelis-Menten saturable (Km, Vmax) and non-saturable (Kd) components of influx. Various computation procedures have been previously reported to estimate the kinetic parameters when an intracarotid injection technique is used. Transformations of the influx data which allow linear plots to obtain estimates were compared with estimates obtained directly from a best fit on a least means squares criterion for both experimental and simulated data. Large discrepancies were apparent between the various estimates of the kinetic parameters when an equal weight was given to transformed data. For pyruvate (21-day-old rats), Km, values varied between 1.02 and 6.25 mM and Vmax varied between 0.68 and 2.30 μmol g−1 min−1. The estimates were almost equivalent when pyruvate data was re-analysed using a weighting scheme based on the finding that the absolute value of the S.D. of influx increased in proportion to influx. It is recommended that estimates of kinetic parameters be obtained by an iterative, non-linear least squares method to fit appropriately weighted data directly.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1979.tb05172.x
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  • 9
    Electronic Resource
    Electronic Resource
    Monitoring Dopamine Metabolism in the Brain of the Freely Moving Rat (1986)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 473 (1986), S. 0 
    Details
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1749-6632.1986.tb23619.x
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  • 10
    Electronic Resource
    Electronic Resource
    Monitoring 5HT Metabolism in the Brain of the Freely Moving Rat (1986)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 473 (1986), S. 0 
    Details
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1749-6632.1986.tb23626.x
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