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  • Methysticin  (2)
  • Alkali metal manganese selenides  (1)
  • 1
    ISSN: 1432-1912
    Keywords: High potassium ; Ictaform events ; Low calcium ; Low magnesium ; Methysticin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Methysticin is one of the constituents of Piper methysticum which possesses anticonvulsant and neuroprotective properties. Its effects on different in vitro seizure models were tested using extracellular recordings in rat temporal cortex slices containing the hippocampus and the entorhinal cortex. Elevating [K+]o0 induced seizure-like events with tonic and clonic electrographic phases in area CA1. Lowering [Ca2+]0 caused recurrent seizure like episodes with large negative field potential shifts. Lowering Mg2+ induced short recurrent discharges in area CA3 and CA1 while ictaform events lasting for many seconds were induced in the subiculum, entorhinal and temporal neocortex. In the hippocampus the activity stayed stable over a number of hours. In contrast, the ictaform events in the subiculum, entorhinal and temporal cortex changed their characteristics after one to two hours to late recurrent discharges. In a concentration-range from 10 to 100 μM methysticin reversibly blocked all these types of epileptiform activity. Decreases in [Ca2+]0 and associated slow field potentials evoked by repetitive stimulation of the stratum radiatum or the alveus remained almost unaffected by methysticin. A paired pulse stimulus paradigm used to test for effects of methysticin on synaptically evoked transient field potentials in normal medium revealed interference with mechanisms involved in frequency potentiation. While responses to alvear stimulation were largely unaffected, the responses to a paired pulse stimulus to stratum radiatum were depressed over the whole range of tested stimulus intervals. The findings suggest that methysticin has effects on different patterns of epileptiform activity possibly by interfering with processes responsible for frequency potentiation.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1912
    Keywords: Key words High potassium ; Ictaform events ; Low calcium ; Low magnesium ; Methysticin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Methysticin is one of the constituents of Piper methysticum which possesses anticonvulsant and neuroprotective properties. Its effects on different in vitro seizure models were tested using extracellular recordings in rat temporal cortex slices containing the hippocampus and the entorhinal cortex. Elevating [K+]0 induced seizure-like events with tonic and clonic electrographic phases in area CA1. Lowering [Ca2+]0 caused recurrent seizure like episodes with large negative field potential shifts. Lowering Mg2+ induced short recurrent discharges in area CA3 and CA1 while ictaform events lasting for many seconds were induced in the subiculum, entorhinal and temporal neocortex. In the hippocampus the activity stayed stable over a number of hours. In contrast, the ictaform events in the subiculum, entorhinal and temporal cortex changed their characteristics after one to two hours to late recurrent discharges. In a concentration-range from 10 to 100 μM methysticin reversibly blocked all these types of epileptiform activity. Decreases in [Ca2+]0 and associated slow field potentials evoked by repetitive stimulation of the stratum radiatum or the alveus remained almost unaffected by methysticin. A paired pulse stimulus paradigm used to test for effects of methysticin on synaptically evoked transient field potentials in normal medium revealed interference with mechanisms involved in frequency potentiation. While responses to alvear stimulation were largely unaffected, the responses to a paired pulse stimulus to stratum radiatum were depressed over the whole range of tested stimulus intervals. The findings suggest that methysticin has effects on different patterns of epileptiform activity possibly by interfering with processes responsible for frequency potentiation.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0044-2313
    Keywords: Alkali metal manganese selenides ; alkali metal manganese tellurides ; crystal structure ; spin structure ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Alkali Metal Manganese Selenides and Tellurides - Synthesis, Crystal and Spin StructuresThe compounds Rb2Mn3Se4, Cs2Mn3Se4, Rb2Mn3Te4 and Cs2Mn3Te4 were synthesized by the reaction of alkali metal carbonates with chalcogen and Mn or MnCO3 in a stream of hydrogen charged with chalcogen.Structural investigations show that all compounds crystallize in isotypic atomic arrangements (Cs2Mn3S4-type, space group Ibam, Z = 4). Additionally neutron diffraction experiments were carried out and yielded the spin structures of Rb2Mn3Se4 and Cs2Mn3Se4 (Shubnikov space group Ibam').The structural related selenides ALiMnSe2 and ALiZnSe2 (A = K, Rb or Cs) were synthesized by analogous reactions. All these compounds are isotypic and crystallize in the BaZn2P2-structure type.
    Notes: Die Verbindungen Rb2Mn3Se4, Cs2Mn3Se4, Rb2Mn3Te4 und Cs2Mn3Te4 wurden durch Umsetzungen von Alkalimetallcarbonaten mit Mangan oder Mangancarbonat und Chalkogen in einem mit Chalkogen beladenen Wasserstoffstrom erhalten.Kristallstrukturuntersuchungen ergaben, daß alle Verbindungen isotyp kristallisieren (Cs2Mn3S4-Typ, Raumgruppe Ibam, Z = 4). Neutronenbeugungsuntersuchungen ermöglichten darüber hinaus die Bestimmung der antiferromagnetischen Spinstrukturen von Rb2Mn3Se4 und Cs2Mn3Se4 (Shubnikov-Raumgruppe Ibam').Die strukturverwandten Selenide ALiMnSe2 und ALiZnSe2 mit A = K, Rb oder Cs wurden über analoge Umsetzungen synthetisiert. Sie kristallisieren alle im BaZn2P2-Typ.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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