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Ann Neurol. 2016 Mar;79(3):354-65. doi: 10.1002/ana.24570. Epub 2016 Feb 13.

Activation of specific neuronal networks leads to different seizure onset types.

Author information

1
Montreal Neurological Institute, Department of Neurology and Neurosurgery, and Department of Physiology, McGill University, Montreal, Quebec, Canada.
2
Douglas Mental Health University Institute, McGill University, Montreal, Quebec, Canada.

Abstract

OBJECTIVE:

Ictal events occurring in temporal lobe epilepsy patients and in experimental models mimicking this neurological disorder can be classified, based on their onset pattern, into low-voltage, fast versus hypersynchronous onset seizures. It has been suggested that the low-voltage, fast onset pattern is mainly contributed by interneuronal (γ-aminobutyric acidergic) signaling, whereas the hypersynchronous onset involves the activation of principal (glutamatergic) cells.

METHODS:

Here, we tested this hypothesis using the optogenetic control of parvalbumin-positive or somatostatin-positive interneurons and of calmodulin-dependent, protein kinase-positive, principal cells in the mouse entorhinal cortex in the in vitro 4-aminopyridine model of epileptiform synchronization.

RESULTS:

We found that during 4-aminopyridine application, both spontaneous seizure-like events and those induced by optogenetic activation of interneurons displayed low-voltage, fast onset patterns that were associated with a higher occurrence of ripples than of fast ripples. In contrast, seizures induced by the optogenetic activation of principal cells had a hypersynchronous onset pattern with fast ripple rates that were higher than those of ripples.

INTERPRETATION:

Our results firmly establish that under a similar experimental condition (ie, bath application of 4-aminopyridine), the initiation of low-voltage, fast and of hypersynchronous onset seizures in the entorhinal cortex depends on the preponderant involvement of interneuronal and principal cell networks, respectively.

PMID:
26605509
PMCID:
PMC4878884
[Available on 2017-03-01]
DOI:
10.1002/ana.24570
[Indexed for MEDLINE]
Free PMC Article

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