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  • 1
    Electronic Resource
    Electronic Resource
    Effects of GABA and bicuculline on N-methyl-D-aspartate- and quisqualate-induced reductions in extracellular free calcium in area CA1 of the hippocampal slice (1986)
    Springer
    Experimental brain research 64 (1986), S. 27-36 
    Details
    ISSN: 1432-1106
    Keywords: Bicuculline ; Calcium ; GABA ; Hippocampus ; NMDA ; Quisqualate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Decreases in extracellular free calcium ([Ca2+]o) and concomitant field potentials were recorded from the dendritic and cell body layers of the CA1 field in transverse hippocampal slices. They were elicited by tetanic stimulation of Schaffer collaterals and commissural fibers or by iontophoretic application of the excitatory amino acids N-methyl-D-aspartate (NMDA) and quisqualate (Quis). Under control conditions, decreases in [Ca2+]o were found to be maximal in stratum pyramidale (SP). In stratum radiatum (SR), 100 μm away from SP, decreases in [Ca2+]o were half the size of those observed in SP. Bicuculline methiodide, bath-applied at concentrations of 10–100 μM, enhanced the reductions in [Ca2+]o, increased the field potentials in all layers and also induced “spontaneous” epileptiform activity. In the presence of bicuculline, the decreases in [Ca2+]o were particularly enhanced in SR and were often greater than those recorded in SP. This was the case for changes in [Ca2+]o induced either by repetitive electrical stimulation or by application of NMDA and Quis. When synaptic transmission was blocked by perfusing the slices with a low Ca2+ medium, all NMDA and Quis-induced changes in [Ca2+]o were predictably reduced but there was a relative enhancement of changes in [Ca2+]o in SR with respect to those in SP. We propose that, under normal conditions, an inhibitory control mediated by GABA limits the reductions of [Ca2+]o particularly in SR. In support of this proposal, we found that bath-applied GABA had a depressant action on changes in [Ca2+]o.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00238198
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  • 2
    Electronic Resource
    Electronic Resource
    Effects of retigabine (D-23129) on different patterns of epileptiform activity induced by 4-aminopyridine in rat entorhinal cortex hippocampal slices (1999)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 359 (1999), S. 33-39 
    Details
    ISSN: 1432-1912
    Keywords: Key words Retigabine ; Anticonvulsant ; Antiepileptic ; New drug ; Field potential ; Bicuculline
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The purpose of this study was to evaluate the effects of the new anticonvulsant drug N-(2-amino-4-[fluorobenzylamino]-phenyl) carbamic acid ethyl ester (retigabine, D-23129, ASTA Medica, Dresden, Germany) on different patterns of epileptiform activity induced by 4-aminopyridine (4AP) in rat entorhinal cortex hippocampal slices. Application of 4AP (100 µM) induced in entorhinal cortex two different types of epileptiform activities; seizure-like events (SLE) and interictal epileptiform discharges (IED). Bicuculline (10 µM) changed 4AP-induced SLE and IED to recurrent epileptiform discharges (RED). IED were isolated after blockade of the SLE by glutamate receptor antagonists for α-amino-3-hydroxy-5-methylisoxazole-4-proprionic acid (AMPA) and N-methyl-d-aspartate (NMDA) receptors, i.e. 1,2,3,4 tetrahydro-6-nitro-2,3-dioxo-benzo[f]quinoxaline-7-sulfonamide (NBQX, 10 µM) and 2-amino-5-phosphonovaleric acid (APV, 30 µM). Anticonvulsant properties of retigabine were evaluated as effect on the frequency and amplitude of SLE, IED and RED. Retigabine suppressed all types of epileptiform events in a dose dependent and reversible manner. SLE were suppressed in 71.4 and 100% of slices by 5 and 10 µM, respectively. The frequency of IED was significantly reduced by 20 µM retigabine (40.9±24.5%) and IED were blocked completely by 50 µM retigabine. When IED were isolated by application of glutamate antagonists 20 µM retigabine was sufficient to block this activity completely. RED induced by combined application of bicuculline and 4AP were blocked in 71.4% of the tested slices with 100 µM retigabine. The frequency of the RED in the remaining slices was reduced by 96.1±6.1%. We conclude that retigabine acts on a large variety of different epileptiform activities in temporal lobe structures that are known to develop readily pharmacoresistant seizures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00005320
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
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