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  • 1
    ISSN: 1435-1463
    Keywords: Keywords: Amantadine ; dopamine D2 receptor ; memantine ; (+)MK-801 ; muscarinic receptor ; NMDA receptor ; receptor autoradiography.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary. Behavioral changes have previously been reported following administrations of uncompetitive NMDA receptor antagonists memantine, amantadine and MK-801 for 14 days, at the doses that produce plasma levels comparable to those seen in patients (20, 100 and 0.31 mg/kg/day respectively). Using the same doses, the effect on receptor binding (autoradiography) was studied in rats. [3H]MK-801 binding was increased in the dentate gyrus and CA3 region of the hippocampus (35.2 and 24.3% respectively) following 3 days S.C. infusion of memantine by ALZET minipumps. One daily injection of memantine for 14 days, increased [3H]MK-801 binding in the frontal cortex by 40.3%. The same treatment with amantadine did increase [3H]raclopride binding to dopamine D2 receptors by 13.5%. None of these treatments changed the expression of muscarinic receptors. It is concluded that subchronic blockade of the NMDA receptor by uncompetitive antagonists at moderate (therapeutically-relevant) doses induced only minor changes in NMDA and dopamine D2 receptor expression.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1435-1463
    Keywords: Keywords: Dopamine ; memantine ; microdialysis ; pharmacokinetics ; pre-frontal cortex.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary. Memantine is an uncompetitive N-methyl-D-aspartate receptor antagonist which blocks the NMDA receptor with moderate-affinity in a use- and voltage dependent manner. In clinical practice it is used chronically in the treatment of dementia and does not induce psychotomimetic effects as, high affinity, uncompetitive antagonists. Thus, it was of interest to determine dopamine (DA) and metabolite (DOPAC – dihydroxyphenylacetic acid and HVA – homovanillic acid) concentrations in the prefrontal cortex (PFC) in response to 14 days administration of memantine (20 mg/kg/day). It was previously determined that in rats this treatment induces sensitization to the locomotor effect and tolerance to the learning impairing properties of high doses of memantine. Acute administration of memantine (20 mg/kg, ip) did not affect dopamine levels in the PFC. It did however increase DA metabolite (DOPAC and HVA) concentrations. Administration of memantine (20 mg/kg/day) for 14 days before the acute challenge only slightly changed memantine's effect on PFC neurochemistry even though pharmacokinetic tolerance was observed. When memantine was administered to the sham group, which had been repeatedly treated with Hypnorm (including neuroleptic), an increase in PFC dopamine and metabolite content was seen. In accordance with the fact that memantine does not possess psychotomimetic activity at therapeutically relevant doses, these experiments showed that it does not affect the prefrontal cortex dopamine levels.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-904X
    Keywords: Microdialysis: experimental brain tumor ; pharmacokinetic ; anticancer drugs ; methotrexate ; histology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. The use of intracerebral microdialysis as a tool to measure the penetration of anticancer agents in brain tumor was investigated. Methods. Following intravenous (iv) administration of 75 mg/kg. concentration-time profiles of methotrexate (MTX) were determined in brain cortical dialysate and in plasma. The individual ratio of the area under the curve of MTX in brain dialysate over that in plasma (MTX penetration) was determined in normal brain, in tumor-bearing brain and in brain after sham tumor implantation. Individual brains were examined histologically on the presence of tumor, as well as for other factors that might influence local MTX penetration. Histological scores were related to the individual data on penetration of MTX. Results. MTX penetration values were higher in cortical brain at the site of the tumor, as compared to the levels measured in normal or sham implanted brain (mean increase to 250 %). In the cortical brain contralateral to the tumor, MTX penetration values were found to be lower than in normal brain (mean reduction of 65 %). Furthermore, it appeared that in the absence of tumor tissue, the presence of exudate around the probe was independently associated with increased penetration of MTX into the brain. Conclusions. Tumor tissue appeared to be the most important parameter in changing local MTX penetration in brain after tumor implantation. In general, it is anticipated that intracerebral microdialysis combined with histological examination can be used to investigate effects of brain tumor presence on regional (periprobe) penetration of anticancer drugs into the brain.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Quality of life research 7 (1998), S. 135-142 
    ISSN: 1573-2649
    Keywords: Quality of Life ; inlammatory bowel disease ; Parkinsons disease ; structural equation modelling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The objective of this study was to examine the structure of disease-specific quality of life (QoL). Models of QoL with either one overall construct or more constructs were tested and the relationships (factor loadings) between the constructs and dimensions were established, using structural equation modelling. The models were tested over time to assess the stability of the structure. To generalize the results further, disease-specific questionnaires of two very different chronic diseases have been compared: inflammatory bowel disease (IBD) and Parkinson's disease (PD). Questionnaires were mailed in 1994 and a repeated measurement was conducted in 1995. Data were obtained from 222 IBD patients and 235 PD patients. The results show that for both diseases, disease-specific QoL can be considered as one construct. The stability over time of the structure of the QoL models was satisfactory. In PD the factor loadings between the dimensions and QoL were within a small range and remained the same over time, while in IBD, the factor loadings had a larger range and fluctuated more. These results imply that one meaningful sum score can be obtained from these questionnaires.
    Type of Medium: Electronic Resource
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