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  • 82.65  (2)
  • Autoreceptors  (2)
  • carbon dioxide  (2)
  • 1
    Digitale Medien
    Digitale Medien
    Effect of chronic administration of the selective serotonin (5-HT) uptake inhibitor citalopram on extracellular 5-HT and apparent autoreceptor sensitivity in rat forebrain in vivo (1995)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 352 (1995), S. 597-606 
    Details
    ISSN: 1432-1912
    Schlagwort(e): Key words Microdialysis ; 5-HT release ; Chronic antidepressant ; Citalopram ; 5-HT reuptake inhibitor ; Tolerance ; Autoreceptors ; Frontal cortex ; Dorsal hippocampus
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract  Rats were administered the selective serotonin (5-HT) uptake blocker citalopram or saline for 14 days to determine if prolonged treatment would lead to changes in extracellular 5-HT or autoreceptor sensitivity. One day after drug withdrawal, dialysis probes were implanted in the frontal cortex and dorsal hippocampus. Dialysis experiments were carried out using chloral hydrate anesthetized rats. The experimental protocol comprised the administration of three consecutive drug challenges: (1) After stable baseline levels were obtained, citalopram was infused through the dialysis probes to locally block uptake in the forebrain. (2) Subsequently, a 5-HT1B receptor agonist (RU24969 or CP93,129) was infused through the probe to test for changes in terminal autoreceptor sensitivity. (3) Last, citalopram was administered systemically to test the effect of indirect activation of somatodendritic autoreceptors. Under these conditions, with uptake already blocked locally in the forebrain, systemic citalopram produces a decrease in extracellular 5-HT, an effect that can be inhibited by pretreatment with antagonists of 5-HT1A receptors. The results indicate that during local infusion of citalopram extracellular 5-HT was significantly higher in the dorsal hippocampus of the chronic citalopram as compared to saline treatment group. This difference persisted throughout the full time course of the experiment. However, the decreases in 5-HT levels produced by local infusion of a 5-HT1B receptor agonist or after systemic citalopram administration were not significantly different between the chronic citalopram and saline treated groups. There were no significant differences between chronic citalopram and saline treated animals in frontal cortex. These results suggest that prolonged inhibition of 5-HT uptake may produce a selective change in the regulation of release from median raphe 5-HT neurons, but this change could not be clearly linked to a change in nerve terminal or somatodendritic autoreceptor sensitivity.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00171317
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  • 2
    Digitale Medien
    Digitale Medien
    Effect of chronic administration of the selective serotonin (5-HT) uptake inhibitor citalopram on extracellular 5-HT and apparent autoreceptor sensitivity in rat forebrain in vivo (1995)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 352 (1995), S. 597-606 
    Details
    ISSN: 1432-1912
    Schlagwort(e): Microdialysis ; 5-HT release ; Chronic antidepressant ; Citalopram ; 5-HT reuptake inhibitor ; Tolerance ; Autoreceptors ; Frontal cortex Dorsal hippocampus
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Rats were administered the selective serotonin (5-HT) uptake blocker citalopram or saline for 14 days to determine if prolonged treatment would lead to changes in extracellular 5-HT or autoreceptor sensitivity. One day after drug withdrawal, dialysis probes were implanted in the frontal cortex and dorsal hippocampus. Dialysis experiments were carried out using chloral hydrate anesthetized rats. The experimental protocol comprised the administration of three consecutive drug challenges: (1) After stable baseline levels were obtained, citalopram was infused through the dialysis probes to locally block uptake in the forebrain. (2) Subsequently, a 5-HT1B receptor agonist (RU24969 or CP93,129) was infused through the probe to test for changes in terminal autoreceptor sensitivity. (3) Last, citalopram was administered systemically to test the effect of indirect activation of somatodendritic autoreceptors. Under these conditions, with uptake already blocked locally in the forebrain, systemic citalopram produces a decrease in extracellular 5-HT, an effect that can be inhibited by pretreatment with antagonists of 5-HT1A receptors. The results indicate that during local infusion of citalopram extracellular 5-HT was significantly higher in the dorsal hippocampus of the chronic citalopram as compared to saline treatment group. This difference persisted throughout the full time course of the experiment. However, the decreases in 5-HT levels produced by local infusion of a 5-HT1B receptor agonist or after systemic citalopram administration were not significantly different between the chronic citalopram and saline treated groups. There were no significant differences between chronic citalopram and saline treated animals in frontal cortex. These results suggest that prolonged inhibition of 5-HT uptake may produce a selective change in the regulation of release from median raphe 5-HT neurons, but this change could not be clearly linked to a change in nerve terminal or somatodendritic autoreceptor sensitivity.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00171317
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Energy accommodation and reactivity of O2 on tungsten (1977)
    Springer
    Applied physics 14 (1977), S. 141-147 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 82.65
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract We have determined by direct molecular beam velocity measurements that translational energy accommodation of O2 molecules scattered from a hot polycrystalline tungsten target is inefficient at high surface temperatures. Translational energy accommodation is inefficient whether the surface is clean or covered with oxygen to a varying extent, even though in the latter case the scattering is diffuse. On a clean tungsten surface the scattering of the O2 was approximately specular and the reaction probability of O2 was constant and greater than 90% over the temperature range 1000K to 2800 K. It was shown by simultaneous helium scattering that atomic surface roughness of an oxygen chemilayer, rather than trapping, is a major cause of the observed diffuse scattering of oxygen. At the lowest surface temperature of 1000 K, with an oxygen chemilayer present, the velocity of the most probable number density of the scattered O2 was lower than in the incoming beam or than that expected for complete equilibration with the surface.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00883081
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  • 4
    Digitale Medien
    Digitale Medien
    Mechanism and speed of initial step of oxygen chemisorption-O2 on W (1977)
    Springer
    Applied physics 14 (1977), S. 411-413 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 82.65
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract A direct first step in the mechanism for the initial oxidation of a polycrystalline tungsten surface, the catalyzed dissociation of O2 on it, or the formation of WO X by O2 at intermediate temperatures is shown to occur in ∼10−13 s. Molecular beam experiments demonstrated that the reactivity was greater than 90%, the unreacted O2 was substantially unaccommodated in translational energy to the surface temperature, and the reaction probability was nearly independent of surface temperature from 2800 to 415 K although there was a small increase at 415 K. The general conditions when no molecular surface precursor state contributes to the surface reactivity are discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00883448
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  • 5
    Digitale Medien
    Digitale Medien
    Impacts of ocean CO2 disposal on marine life: II. Probabilistic plume exposure model used with a time‐varying dose‐response analysis (1997)
    Springer
    Environmental modeling and assessment 2 (1997), S. 345-353 
    Details
    ISSN: 1573-2967
    Schlagwort(e): carbon dioxide ; plume ; pH ; random walk ; diffusion
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Energietechnik
    Notizen: Abstract A method to evaluate aquatic mortality given a pollutant distribution is presented and applied to several sample low pH plumes representing various ocean CO2 disposal schemes. The method is an improvement over current analysis because it integrates the mortality due to time‐varying exposure to low pH with the probabilistic experiences of passive organisms subject to turbulent lateral diffusion as they pass through the plume. For the examples presented, the plume was discretized laterally into lanes and longitudinally by time steps, and a random walk model accounting for the scale‐dependent nature of relative diffusion was used to simulate the organism pathways over one time step. From these simulations, the probability that an organism will be in a given lane, $$\dot \jmath $$ , one time step after it starts from an initial lane, $$i$$ , was determined for all combinations of $$i$$ and $$\dot \jmath $$ . These probabilities were used to find the number of organisms following each of the possible pathways, and the mortality to the organisms due to their time varying exposure to low pH was determined by using the toxicity model described in part I of this paper. The integrated method allows the impact of the plume to be described in terms of total organism mortality as well as spatial deficit of organisms.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1019081915826
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  • 6
    Digitale Medien
    Digitale Medien
    Impacts of ocean CO2 disposal on marine life: I. A toxicological assessment integrating constant‐concentration laboratory assay data with variable‐concentration field exposure (1997)
    Springer
    Environmental modeling and assessment 2 (1997), S. 333-343 
    Details
    ISSN: 1573-2967
    Schlagwort(e): carbon dioxide ; sequestration ; plume ; pH ; toxicity ; zooplankton
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Energietechnik
    Notizen: Abstract Feasibility studies suggest that the concept of capturing CO2 from fossil fuel power plants and discharging it to the deep ocean could help reduce atmospheric CO2 concentrations. However, the local reduction in seawater pH near the point of injection is a potential environmental impact. Data from the literature reporting on toxicity of reduced pH to marine organisms potentially affected by such a plume were combined into a model expressing mortality as a function of pH and exposure time. Since organisms exposed to real plumes would experience a time‐varying pH, methods to account for a variable exposure were reviewed and a new method developed based on the concept of isomortality. In part II of this paper, the method is combined with a random‐walk model describing the transport of passive organisms through a low pH plume leading to a Monte‐Carlo‐like risk assessment which is applied to several candidate CO2 injection scenarios.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1019029931755
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