Effects of NMDA antagonists on picrotoxin-, low Mg2+- and low Ca2+-induced epileptogenesis and on evoked changes in extracellular Na+ and Ca2+ concentrations in rat hippocampal slices

doi:10.1016/0920-1211(89)90003-X

Epilepsy Research

Volume 4, Issue 3, November–December 1989, Pages 187-200

https://doi.org/10.1016/0920-1211(89)90003-X Get rights and content

Abstract

The anticonvulsant properties of ketamine and 2-APV were compared on 3 types of convulsant activity in hippocampal area CA1: the ‘picrotoxin-epilepsy,’ the ‘low magnesium epilepsy’ and the ‘low calcium epilepsy.’ In particular the spontaneous activity, the synaptically evoked responses and the changes in [Ca²⁺]₀ were examined, since in many cases of epilepsy, Ca²⁺ uptake into cells is enhanced.

In normal medium, ketamine and 2-APV have nearly no effect on stimulus evoked decreases in [Ca²⁺]₀, although they clearly depress NMDA-induced ionic changes. However, ketamine and 2-APV prevent to some extent the augmentation of stimulus-induced changes in [Ca²⁺]₀, observed after treating slices with picrotoxin or Mg²⁺-free medium. This extra Ca²⁺ uptake is probably mediated by NMDA operated channels. Our findings also show that ketamine, like 2-APV, has a stronger anticonvulsant effect on the low Mg-than on the picrotoxin-induced epileptiform activity. Responses to iontophoretically applied NMDA are facilitated in the ‘low calcium epilepsy’ and can be selectively blocked by ketamine. Spontaneous epileptiform activity occurring in low calcium can be blocked by ketamine only when some synaptic transmission is still present.

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Research reportEffects of NMDA antagonists on picrotoxin-, low Mg2+- and low Ca2+-induced epileptogenesis and on evoked changes in extracellular Na+ and Ca2+ concentrations in rat hippocampal slices

Abstract

Brain Res.

Epilepsy Res.

Brain Res.

Brain Res.

Neurosci. Lett.

Neurosci. Lett.

Neurosci. Lett.

Brain Res.

Neurosci. Lett.

Neurosci. Lett.

Brain Res.

Neuroscience

Brain Res.

Neuroscience

Brain Res.

Eur. J. Pharmacol.

Brain Res.

Neuropharmacology

Brain Res.

Epilepsy Res.

Neuroscience

Neurosci. Lett.

Ion-Selective Microelectrodes

Selective depression of excitatory amino acid induced depolarizations by magnesium ions in isolated spinal cord preparations

J. Physiol. (Lond.)

Mechanisms for low-calcium, high-magnesium-synchronous burst in the in vitro hippocampal slice

Anticonvulsant action of excitatory amino acid antagonists

Science

Stimulus-induced changes in extracellular Na+ and Cl− concentration in relation to changes in the size of the extracellular space

Exp. Brain Res.

Involvement of N-methyl-d-aspartate receptors in epileptiform bursting in the rat hippocampal slice

J. Physiol. (Lond.)

The role of calcium ions in tetanic and post-tetanic increase of miniature end-plate potential frequency

J. Physiol. (Lond.)

Mechanisms of neocortical epileptogenesis in vitro

J. Neurophysiol.

Low-calcium field burst discharges of CA1 pyramidal neurones in rat hippocampal slices

J. Physiol. (Lond.)

Picrotoxin induced epileptiform activity in hippocampus: role of endogenous versus synaptic factors

J. Neurophysiol.

Research report
Effects of NMDA antagonists on picrotoxin-, low Mg²⁺- and low Ca²⁺-induced epileptogenesis and on evoked changes in extracellular Na⁺ and Ca²⁺ concentrations in rat hippocampal slices

Stimulus-induced changes in extracellular Na⁺ and Cl⁻ concentration in relation to changes in the size of the extracellular space

Involvement of $N- methyl- d -aspartate$ receptors in epileptiform bursting in the rat hippocampal slice