Effects of the epileptogenic agent bicuculline methiodide on membrane currents induced byN-methyl-d-aspartate and kainate (oocyte;Xenopus laevis)

Muβhoff, U.; Madeja, Michael; Bloms–Funke, Petra; Speckmann, Erwin‐Josef

doi:10.1016/0006-8993(94)91773-6

Cited by 13 publications

(7 citation statements)

References 16 publications

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“…This conflicts with the predictions of a model involving competition between NMDA and 5-MeOT, but can be explained by non-competitive models involving open channel block. In a similar way, bicuculline methiodide has been shown to reduce NMDA responses in a non-competitive way; however, the voltage-dependence of this block was not as clear (see Wright & Nowak, 1992;MuBhoff et al, 1994).…”

Section: An Open Channel Block Could Account For Our Resultsmentioning

confidence: 99%

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Voltage‐dependent block of NMDA responses by 5‐HT agonists in ventral spinal cord neurones

Chesnoy-Marchais

Barthe

1996

British J Pharmacology

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1 Modulation by 5-hydroxytryptamine receptor agonists of the NMDA responses of ventral spinal cord neurones was studied by use of the whole-cell patch-clamp technique. 2 In a Mg-free solution containing tetrodotoxin and glycine, 5-hydroxytryptamine (5-HT, 10-100 ,UM) reduced the NMDA response, the block increasing with hyperpolarization. Kainate responses were little affected. 3 Some classical agonists of 5-HT receptors induced similar blocking effects. At 10 IM, both a selective agonist of 5-HT2 receptors, (±)-2,5-dimethoxy-4 iodo amphetamine (DOI), and a selective agonist of some 5-HTI receptors, (±)-8-hydroxy-2(n-dipropyl amino) tetralin (8-OH-DPAT), induced pronounced blocking effects, of 48% and 33% respectively at -100 mV, whereas another 5-HT1 agonist, 5-carboxamidotryptamine (5-CT) was ineffective. At 100 gIM, 5-methoxytryptamine (5-MeOT) induced a complete block of the NMDA responses recorded at -100 mV. The order of potency was: 5-MeOT DOI> 8-OH-DPAT > 5-HT > 5-CT. 4 Neither spiperone nor ketanserin (1 riM) prevented the blocking effect of 5-HT or DOI. 5 Prolonged preincubations with 5-HT did not block the response if NMDA was applied without 5-HT. When 5-HT agonists were applied both by preincubation and with NMDA, the degree of block increased during the NMDA application.6 Lowering the NMDA concentration (from 100 to 20 giM) slightly decreased the blocking effect of 5-MeOT. 7 External Mg2+ ions (1 mM) also reduced the blocking effects of 5-HT and 5-MeOT. 8 The blocking effects described appear to be independent of classical 5-HT receptors. Their voltagedependence suggests a mechanism of open channel block consistent with all the results obtained.

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Section: An Open Channel Block Could Account For Our Resultsmentioning

confidence: 99%

“…In a similar way, bicuculline methiodide has been shown to reduce NMDA responses in a non-competitive way; however, the voltage-dependence of this block was not as clear (see Wright & Nowak, 1992;MuBhoff et al, 1994).…”

Section: Perfusion Systemmentioning

confidence: 99%

Voltage‐dependent block of NMDA responses by 5‐HT agonists in ventral spinal cord neurones

Chesnoy-Marchais

Barthe

1996

British J Pharmacology

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“…Injection of mRNA into the oocytes led to the functional expression of various ligand-operated ion channels sensitive to the neurotransmitters ␥-aminobutyric acid, dopamine, serotonin, and glutamate with its agonists kainate, quisqualate, and N-methyl-D-aspartate, and AMPA (data not shown; see Mußhoff et al, 1994). The administration of melatonin to the mRNA-injected oocytes evoked oscillatory inward currents ( Fig.3A; n ϭ 61), whereas native oocytes or water-injected oocytes did not respond to either melatonin or other neurotransmitters (data not shown; see Fischer et al, 1996).…”

Section: Xenopus Oocytesmentioning

confidence: 92%

Melatonin receptors in rat hippocampus: molecular and functional investigations

et al. 2002

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Since binding sites for melatonin have been found in the hippocampus of several mammals, it has been suggested that the pineal hormone melatonin is able to modulate neuronal functions of hippocampal cells. In order to get more insight into the role of melatonin for the functions of hippocampal cells, the following experiments were performed: male rats, maintained under a 12/12-h light-dark cycle, were sacrificed by decapitation at zeitgeber times (h) ZT2, ZT8, and ZT15 (ZT0 = lights on); for experiment 1, gene expression for melatonin receptors was detected in the hippocampus and in hippocampal subfields by means of the RT-PCR technique; for experiment 2, electrophysiological and pharmacological properties of melatonin receptors heterologously expressed in Xenopus oocytes after injection of mRNA from the hippocampus were analyzed by means of voltage clamp technique; and for experiment 3, effects of melatonin on the spontaneous firing rate of action potentials in the CA1 regions of hippocampal slices were analyzed by means of extracellular recordings. The RT-PCR data revealed that transcripts for both the MT1 and MT2 melatonin receptors are present in the dentate gyrus, CA3, and CA1 regions, and the subiculum of the hippocampus. Injection of mRNA from rat hippocampus into the Xenopus oocytes led to the functional reconstitution of melatonin-sensitive receptors, which activates calcium-dependent chloride inward currents. The melatonin responses were abolished by simultaneous administration of the antagonists 2-phenylmelatonin and luzindole, and were unaffected by the MT2 antagonist 4-phenyl-2-propionamidotetralin. Bath-applied melatonin (1 micromol/l) enhances the firing rate of neurons in the CA1 region. The effect was small in experiments performed at ZT8 (<2 times the initial level) and large in experiments performed at ZT15 (>6 times). The changes of neuronal firing rate induced by melatonin were completely suppressed with simultaneous administration of the melatonin receptor antagonist luzindole (10 micromol/l). The results indicate that melatonin may play an important role in modulating neuronal excitability in the hippocampus.

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“…The nonspecific binding was near the background. screening demonstrated that the injected oocytes expressed receptors sensitive to the neurotransmitters gamma-aminobutyric acid, glutamate, dopamine and serotonine (data not shown; [18,19]). The administration of MEL to the RNA-injected oocytes evoked oscillatory inward currents ( Fig.…”

Section: Pattern Of Mel Binding Sites In the Rat Brainmentioning

confidence: 99%

Expression and functional characterization of a melatonin‐sensitive receptor in Xenopus oocytes

Fischer¹,

Muβhoff²,

Fauteck³

et al. 1996

FEBS Letters

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Effects of the epileptogenic agent bicuculline methiodide on membrane currents induced byN-methyl-d-aspartate and kainate (oocyte;Xenopus laevis)

Cited by 13 publications

References 16 publications

Voltage‐dependent block of NMDA responses by 5‐HT agonists in ventral spinal cord neurones

Voltage‐dependent block of NMDA responses by 5‐HT agonists in ventral spinal cord neurones

Melatonin receptors in rat hippocampus: molecular and functional investigations

Expression and functional characterization of a melatonin‐sensitive receptor in Xenopus oocytes

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