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  • 1
    Electronic Resource
    Electronic Resource
    Transmembrane 36CI− Flux Measurements and Desensitization of the γ-Aminobutyric AcidA Receptor (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: Some data on the concentration range of response and the concentration for half-response (EC50) of γ-aminobutyric acid (GABA) for the GABAA receptor are reviewed and compared. An analysis of the 36CI− flux assay demonstrates that both the EC50 and the slope of a Hill plot depend on the ion influx or efflux assay time. The effects of depletion of the 36CI− concentration gradient during the assay and of receptor desensitization on the result for a range of assay times are considered. The EC50 can be decreased by orders of magnitude by increasing the assay time. The EC50 measured in a finite time is less than the half-response concentration for the response(s) of the receptor. The extent of this difference depends on the receptor concentration per internal volume. The maximal decrease of EC50 depends on the rate of receptor desensitization. The computer simulations showed that a GABAA receptor with a half-response concentration of 100 μM GABA can give 36CI− flux measurements with an EC50 value 100-fold lower.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1990.tb03110.x
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  • 2
    Electronic Resource
    Electronic Resource
    High-frequency synaptic input contributes to seizure initiation in the low-[Mg2+] model of epilepsy (2004)
    Oxford, UK : Blackwell Science, Ltd
    European journal of neuroscience 19 (2004), S. 0 
    Details
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: High-frequency field potential activity between 50 and 400 Hz occurs throughout seizure-like events recorded from the CA3 region of juvenile rat hippocampal slices under low-[Mg2+] condition. Another (400–800 Hz) component occurred mainly during preictal paroxysmal spiking and the onsets of seizure-like events (97%) and less frequently during tonic and clonic phases (38% and 70%, respectively). Short epochs of oscillations in this range were associated with fast negative field potential deflections at the start of field potential transients. Voltage-clamp recordings from putative CA3 pyramidal cells showed the occurrence of synaptic inputs in the same frequency range at the onset of seizure-like events and the beginning of preictal or clonic paroxysmal spikes, while the frequency of action potentials never reached that range. The amplitude of fast negative field potential deflection, the rise time of membrane potential or voltage-clamp current changes and the mean phase coherence were consistent with an increase of synchronization towards the onset of a seizure-like event. Their parallel changes indicate the involvement of both synaptic and nonsynaptic mechanisms in the synchronization of neuronal activity and the development of seizure-like events in the low-[Mg2+] model of epilepsy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-9568.2004.03231.x
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  • 3
    Electronic Resource
    Electronic Resource
    Coupled intra- and extracellular Ca2+ dynamics in recurrent seizure-like events (2000)
    Oxford, UK : Blackwell Science Ltd
    European journal of neuroscience 12 (2000), S. 0 
    Details
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: We considered the evolution of Ca2+ oscillation dynamics in recurrent seizure-like events. Dynamic system behaviour was characterized in the state space reconstructed from intra- and extracellular [Ca2+] fluctuations simultaneously measured in cultured rat hippocampal slices under low-[Mg2+] conditions. When associated in the seizure-like event, these fluctuations occurred on a restricted set, the attractor, embedded in the full state space with less than five degrees of freedom. Instantaneous relative phase differences indicated field potential-driven phase jumps locked onto seizure-like events. To account for recurrent dynamics, calculations were performed on different extensions of a model for Ca2+ oscillation. These identified bidirectional, asymmetrical coupling of extracellular with intracellular (cytosolic, Ca2+ store, mitochondrial) Ca2+ dynamics as critical in its development.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-9568.2000.00284.x
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  • 4
    Electronic Resource
    Electronic Resource
    Possible Involvement of GABAA and GABAB Receptors in the Inhibitory Action of Lindane on Transmitter Release from Cerebellar Granule Neurons (1999)
    Springer
    Neurochemical research 24 (1999), S. 1189-1193 
    Details
    ISSN: 1573-6903
    Keywords: GABA receptors ; lindane, transmitter release
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Cerebellar granule cells in culture express receptors for GABA belonging to the GABAA and GABAB classes. In order to characterize the ability of the insecticide lindane to interact with these receptors cells were grown in either plain culture media or media containing 150 μM THIP as this is known to influence the properties of both GABAA and GABAB receptors. It was found that lindane regardless of the culture condition inhibited evoked (40 mM K+) release of neurotransmitter ([3H]D-aspartate as label for glutamate). In naive cells both GABAA and GABAB receptor active drugs prevented the inhibitory action of lindane but in THIP treated cultures none of the GABAA and GABAB receptor active drugs had any effect on the inhibitory action of lindane. This lack of effect was not due to inability of baclofen itself to inhibit transmitter release. It is concluded that lindane dependent on the state of the GABAA and GABAB receptors is able to indirectly interfere with both GABAA and GABAB receptors. In case of the latter receptors it was shown using [3H]baclofen to label the receptors that lindane could not displace the ligand confirming that lindane is likely to exert its action at a site different from the agonist binding site.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1020724823117
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  • 5
    Electronic Resource
    Electronic Resource
    Methiodide of the GABA antagonist (+)-bicuculline is levorotatory (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 1 (1989), S. 178-179 
    Details
    ISSN: 0899-0042
    Keywords: CD spectra ; optical rotation ; phthalideisoquinoline base and salts ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The appearance of positive charge on the nitrogen moiety of phthalideisoquinoline alkaloids brings about a strong change in the intensities of CD Cotton effects. Hence the optical rotations of enantiomeric salts and their parent base of identical configuration are often of opposite sign. Thus, the name (+)-bicuculline-methiodide for the methiodide salt of (+)-bicuculline is false.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530010214
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  • 6
    Electronic Resource
    Electronic Resource
    Stereoselective binding of benzodiazepines and related compounds on calmodulin-sepharose (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 69-73 
    Details
    ISSN: 0899-0042
    Keywords: chiral interaction ; affinity chromatography ; benzodiazepines ; phenothiazines ; calcium antagonists ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A method has been presented to evaluate the Ca2+-dependent binding affinity of ligands to calmodulin (CaM) from their chromatographic retentions obtained on a CaM-Sepharose column. Enantiomers of benzodiazepines and related compounds could be separated. Among chiral calcium antagonists, verapamil showed stereoselectivity of binding. © 1995 Wiley-Liss, Inc.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530070204
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