Regional and time dependent variations of low Mg 2+ induced epileptiform activity in rat temporal cortex slices

Regional and time dependent variations of low Mg 2+ induced epileptiform activity in rat temporal... 221 87 87 3 3 J. P. Dreier U. Heinemann Institute of Neurophysiology, Center of Physiology and Pathophysiology, University at Cologne Robert-Koch-Str. 39 41 Köln Federal Republic of Germany Summary In order to study spatial interactions during low magnesium induced epileptiform activity, changes in extracellular potassium concentration ((K + ) o ) and associated slow field potentials (f.p.'s) were recorded in thin rat temporal cortex slices (400 μ m) containing the neocortical temporal area 3 (Te3), the entorhinal cortex (EC) and the hippocampal formation with the dentate gyrus, area CA3 and CA1 and the subiculum (Sub). The epileptiform activity was characterized by short recurrent epileptiform discharges (40 to 80 ms, 20/min) in areas CA3 and CA1 and by interictal discharges and tonic and clonic seizure like events (SLE's) (13–88s) in the EC, Te3 and Sub. While interictal discharges occurred independent of each other in the different subfields, the three areas became synchronized during the course of a SLE. The EC, Te3 and Sub all could represent the “focus” for generation of the SLE's. This initiation site for SLE's sometimes changed from one area to another. The characteristics of the rises in (K + ) o and subsequent undershoots were comparable to previous observations in in vivo preparations. Interestingly, rises in (K + ) o could start before actual onset of seizure like activity in secondarily recruited areas. The epileptiform activity could change its characteristics to either a state of recurrent tonic discharge episodes or to a continuous clonic discharge state reminiscent of various forms of status epilepticus. We did not observe, in any of these states, active participation by area CA3 in the epileptiform activity of the EC in spite of clear projected activity to the dentate gyrus. Even after application of picrotoxin (20 μ M), area CA3 did not actively participate in the SLE's generated in the entorhinal cortex. When baclofen (2 μ M) was added to the picrotoxin containing medium, SLE's occurred both in the entorhinal cortex and in area CA3, suggesting that inhibition of inhibitory interneurons by baclofen could overcome the “filtering” of projected activity from the entorhinal cortex to the hippocampus. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Experimental Brain Research Springer Journals

Regional and time dependent variations of low Mg 2+ induced epileptiform activity in rat temporal cortex slices

Experimental Brain Research, Volume 87 (3) – Dec 1, 1991

Loading next page...
 
/lp/springer-journals/regional-and-time-dependent-variations-of-low-mg-2-induced-jFJD0N6NVN
Publisher
Springer Journals
Copyright
Copyright © 1991 by Springer-Verlag
Subject
Biomedicine; Neurosciences; Neurology
ISSN
0014-4819
eISSN
1432-1106
DOI
10.1007/BF00227083
Publisher site
See Article on Publisher Site

Abstract

221 87 87 3 3 J. P. Dreier U. Heinemann Institute of Neurophysiology, Center of Physiology and Pathophysiology, University at Cologne Robert-Koch-Str. 39 41 Köln Federal Republic of Germany Summary In order to study spatial interactions during low magnesium induced epileptiform activity, changes in extracellular potassium concentration ((K + ) o ) and associated slow field potentials (f.p.'s) were recorded in thin rat temporal cortex slices (400 μ m) containing the neocortical temporal area 3 (Te3), the entorhinal cortex (EC) and the hippocampal formation with the dentate gyrus, area CA3 and CA1 and the subiculum (Sub). The epileptiform activity was characterized by short recurrent epileptiform discharges (40 to 80 ms, 20/min) in areas CA3 and CA1 and by interictal discharges and tonic and clonic seizure like events (SLE's) (13–88s) in the EC, Te3 and Sub. While interictal discharges occurred independent of each other in the different subfields, the three areas became synchronized during the course of a SLE. The EC, Te3 and Sub all could represent the “focus” for generation of the SLE's. This initiation site for SLE's sometimes changed from one area to another. The characteristics of the rises in (K + ) o and subsequent undershoots were comparable to previous observations in in vivo preparations. Interestingly, rises in (K + ) o could start before actual onset of seizure like activity in secondarily recruited areas. The epileptiform activity could change its characteristics to either a state of recurrent tonic discharge episodes or to a continuous clonic discharge state reminiscent of various forms of status epilepticus. We did not observe, in any of these states, active participation by area CA3 in the epileptiform activity of the EC in spite of clear projected activity to the dentate gyrus. Even after application of picrotoxin (20 μ M), area CA3 did not actively participate in the SLE's generated in the entorhinal cortex. When baclofen (2 μ M) was added to the picrotoxin containing medium, SLE's occurred both in the entorhinal cortex and in area CA3, suggesting that inhibition of inhibitory interneurons by baclofen could overcome the “filtering” of projected activity from the entorhinal cortex to the hippocampus.

Journal

Experimental Brain ResearchSpringer Journals

Published: Dec 1, 1991

There are no references for this article.

You’re reading a free preview. Subscribe to read the entire article.


DeepDyve is your
personal research library

It’s your single place to instantly
discover and read the research
that matters to you.

Enjoy affordable access to
over 18 million articles from more than
15,000 peer-reviewed journals.

All for just $49/month

Explore the DeepDyve Library

Search

Query the DeepDyve database, plus search all of PubMed and Google Scholar seamlessly

Organize

Save any article or search result from DeepDyve, PubMed, and Google Scholar... all in one place.

Access

Get unlimited, online access to over 18 million full-text articles from more than 15,000 scientific journals.

Your journals are on DeepDyve

Read from thousands of the leading scholarly journals from SpringerNature, Elsevier, Wiley-Blackwell, Oxford University Press and more.

All the latest content is available, no embargo periods.

See the journals in your area

DeepDyve

Freelancer

DeepDyve

Pro

Price

FREE

$49/month
$360/year

Save searches from
Google Scholar,
PubMed

Create folders to
organize your research

Export folders, citations

Read DeepDyve articles

Abstract access only

Unlimited access to over
18 million full-text articles

Print

20 pages / month

PDF Discount

20% off