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  • 1
    Electronic Resource
    Electronic Resource
    Blood-Brain Transfer of l-Phenylalanine Declines After Peripheral but Not Central Nervous Administration of Vasopressin (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: To determine whether a previously reported effect of vasopressin on blood-brain transfer of leucine extends to other large neutral amino acids, we measured the regional blood-brain transfer of l-phenylalanine with the integral technique. Intravenous co-injection of l-phenylalanine and arginine vasopressin (30 nmol to 10 pmol) resulted in a decrease of the permeability-surface area (PaS) product of phenylalanine of between 11 and 39%. In addition, the peptide elicited a decrease of the cerebral blood flow of between 11 and 56% combined with a drastic decrease of the cardiac output (32–64%) and an elevation of the blood pressure to ∼150% of control values. However, we found no changes of the cardiac output, the blood pressure, or the PaS product of phenylalanine after microdialysis (30 min, 5 μl min−1) of arginine vasopressin (15 μmol l−1) into the dorsal hippocampus, but cerebral blood flow was decreased. The results support the hypothesis that arginine vasopressin receptors at the blood-brain barrier are involved in the regulation of large neutral amino acid transfer from blood to brain and indicate that these receptors are located at the luminal membrane of the endothelial cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1990.tb05801.x
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  • 2
    Electronic Resource
    Electronic Resource
    Effects of Vasopressin on Blood-Brain Transfer of Methionine in Dogs (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 59 (1992), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: We used a simplified probe detection system for positron-emitting radionuclides in order to measure blood-brain barrier transport of amino acids in anesthetized dogs. Plasma and brain time-activity curves were recorded after intravenous bolus injection of L-[11C]methionine before and after administration of 1 μg of vasopressin. Three-compartment models with three or four transfer coefficients were used to derive the kinetics of L-[11C]methionine uptake in brain. The blood-brain clearance of the tracer (K1) was 0.075 ml ml-1 min-1 before and 0.041 ml ml-1 mir-1 after injection of vasopressin. The partition volume and the initial distribution (plasma) volume of methionine were unchanged and within the expected limits. The net accumulation rate of methionine (K), estimated by both the four-parameter (kinetic) and three-parameter (graphic) approaches, decreased after vasopressin injection in all six studies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1992.tb08456.x
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  • 3
    Electronic Resource
    Electronic Resource
    Decrease of Extracellular Taurine in the Rat Dorsal Hippocampus After Central Nervous Administration of Vasopressin (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 58 (1992), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: The extracellular amino acid concentrations in the left and right dorsal hippocampus of male rats were studied before and during application of vasopressin into the right hippocampus. The method of intracerebral microdialysis was used for both arginine vasopressin administration and monitoring of the composition of the extracellular fluid. The concentrations of 16 amino acids were measured by HPLC in the perfusate samples. The level of taurine declined 20% in the right hippocampus during perfusion with vasopressin, whereas o-phosphoethanolamine decreased in both sides, the left 20% and the right 24%. These alterations may be related to cerebral osmoregulation. Also, the levels of tyrosine and phenylalanine increased 15% and 35%, respectively, during administration of vasopressin. No changes of other amino acids were observed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1992.tb11359.x
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  • 4
    Electronic Resource
    Electronic Resource
    Changes in Regional Blood–Brain Transfer of l-Leucine Elicited by Arginine-Vasopressin (1986)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 46 (1986), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Arginine-vasopressin (AVP), injected into the carotid artery in physiological concentration together with L-leucine, changed kinetic constants of the blood—brain barrier (BBB) transport of this neutral amino acid without changing the cerebral blood flow (CBF). The maximum velocity of transport (Vmax), the half-saturation constant (Km), the nonsaturable transport constant (KD), and CBF were estimated in nine brain regions of male Wistar rats anesthetized with ether. In cerebral hemisphere, Vmax decreased from 21 nmol min−1. g−1 (control) to 7.6 nmol. min−1. g−1 (AVP). Km decreased from 0.11 to 0.029 mM. Regional differences of the kinetic constants were found in controls as well as in AVP-treated animals. In all regions, the calculated constants Vmax and Km of animals coinjected with AVP were significantly decreased when compared to controls. A direct or indirect interaction of AVP with the transport system of large neutral amino acids is suggested.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1986.tb13000.x
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  • 5
    Electronic Resource
    Electronic Resource
    Functional Expression of the Serotonin Transporter in Immortalized Rat Brain Microvessel Endothelial Cells (2000)
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 74 (2000), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: There is evidence from recent studies that the brain endothelium (of capillaries and/or larger vessels) may serve as a specific target for serotonin [5-hydroxytryptamine (5-HT)]. This neurotransmitter is expected to be involved in the regulation of the blood-brain barrier (BBB) permeability and/or of the cerebral blood flow via receptor-mediated mechanisms. Effective control of these processes depends on a speedy uptake and metabolism of released 5-HT molecules. To realize this, a similar mechanism of 5-HT uptake as in brain may exist at the BBB. In this study, we have demonstrated using RT-PCR that 5-HT transporter mRNA is present in the brain endothelium and that a saturable transport system for 5-HT is functionally expressed in immortalized rat brain endothelial cells (RBE4 cells). These cells take up [3H]5-HT by an active saturable process with a Km value of 397 ± 64 nmol/L and a transport capacity of 51.7 ± 3.5 pmol · g-1· min-1. The 5-HT uptake depends on Na+, as indicated by the replacement of NaCl by LiCl. The 5-HT uptake was sensitive to specific 5-HT transport inhibitors such as paroxetine, clomipramine, fluoxetine, and citalopram but not to inhibitors of the vesicular amine transporter such as reserpine or tetrabenazine. Our results demonstrate that cerebral endothelial cells are able to participate actively in the removal and metabolism of the released 5-HT, which supports the concept of direct serotoninergic regulation of the BBB function.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1471-4159.2000.741241.x
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  • 6
    Electronic Resource
    Electronic Resource
    Structural modification of receptor-binding technetium-99m complexes in order to improve brain uptake (1997)
    Springer
    European journal of nuclear medicine 24 (1997), S. 316-319 
    Details
    ISSN: 1619-7089
    Keywords: Key words: Blood-brain barrier ; Brain uptake ; Serotonin receptor binding ; technetium-99m complexes ; pKa values ; Lipophilicity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. Low brain uptake is a generally accepted problem in developing technetium-99m brain receptor imaging agents. For a class of potential 5-HT2A receptor-binding agents we tried to improve the original low brain uptake of 0.4% injected dose (ID) in rats 5 min p.i. by modifying the lipophilic properties of the molecules. Because of the presence of a protonable nitrogen, which according to the pK a value leads to ionization of the molecule at blood pH, the pK a value was considered to be the parameter most suitable for adjustment of lipophilicity. Insertion of ether-oxygen in the molecule of five candidates lowers the apparent pK a value from 10.0 to 8.3 and dramatically increases the brain uptake to 1.3% ID at 5 min. The direct relationship between brain uptake and apparent pK a cannot be simply explained by the increase in the pK a-governed proportion of the neutral species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01728770
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  • 7
    Electronic Resource
    Electronic Resource
    Structural modification of receptor-binding technetium-99m complexes in order to improve brain uptake (1997)
    Springer
    European journal of nuclear medicine 24 (1997), S. 316-319 
    Details
    ISSN: 1619-7089
    Keywords: Blood-brain barrier ; Brain uptake ; Serotonin receptor binding ; technetium-99m complexes ; pK a values ; Lipophilicity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Low brain uptake is a generally accepted problem in developing technetium-99m brain receptor imaging agents. For a class of potential 5-HT2A receptorbinding agents we tried to improve the original low brain uptake of 0.4% injected dose (ID) in rats 5 min p.i. by modifying the lipophilic properties of the molecules. Because of the presence of a protonable nitrogen, which according to the pK a value leads to ionization of the molecule at blood pH, the pK a value was considered to be the parameter most suitable for adjustment of lipophilicity. Insertion of ether-oxygen in the molecule of five candidates lowers the apparent pK a value from 10.0 to 8.3 and dramatically increases the brain uptake to 1.3% ID at 5 min. The direct relationship between brain uptake and apparent pK a cannot be simply explained by the increase in the pK a-governed proportion of the neutral species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01728770
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
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