title: Epileptiform synchronization and high-frequency oscillations in brain slices comprising piriform and entorhinal cortices.
abstract: We employed field potential recordings in extended in vitro brain slices form Sprague-Dawley rats containing the piriform and entorhinal cortices (PC and EC, respectively) to identify the characteristics of epileptiform discharges and concomitant high-frequency oscillations (HFOs, ripples: 80-200Hz, fast ripples: 250-500Hz) during bath application of 4-aminopyridine (4AP, 50μM). Ictal-like discharges occurred in PC and EC either synchronously or independently of each other; synchronous ictal discharges always emerged from a synchronous "fast" interictal background whereas asynchronous ictal discharges were preceded by a "slow" interictal event. In addition, asynchronous ictal discharges had longer duration and interval of occurrence than synchronous ictal discharges, and contained a higher proportion of ripples and fast ripples. Cutting the connections between PC and EC made synchronicity disappear and increased ictal discharges duration in the EC but failed in changing HFO occurrence in both areas. Finally, antagonizing ionotropic glutamatergic receptors abolished ictal activity in all experiments, increased the duration and rate of occurrence of interictal discharges occurring in PC-EC interconnected slices while it did not influence the slow asynchronous interictal discharges in both areas. Our results identify some novel in vitro interactions between olfactory (PC) and limbic (EC) structures that presumably contribute to in vivo ictogenesis as well.
authors.affiliation: Montreal Neurological Institute, Department of Neurology & Neurosurgery, McGill University, 3801 University Street, Montréal, QC H3A 2B4, Canada.
authors.forename: S
authors.initials: S
authors.lastname: Hamidi
authors.affiliation: Montreal Neurological Institute, Department of Neurology & Neurosurgery, McGill University, 3801 University Street, Montréal, QC H3A 2B4, Canada.
authors.forename: M
authors.initials: M
authors.lastname: Lévesque
authors.affiliation: Montreal Neurological Institute, Department of Neurology & Neurosurgery, McGill University, 3801 University Street, Montréal, QC H3A 2B4, Canada. Electronic address: massimo.avoli@mcgill.ca.
authors.forename: M
authors.initials: M
authors.lastname: Avoli
mesh_terms: D015761:4-Aminopyridine / Q000494:pharmacology; D000818:Animals; D004195:Disease Models, Animal; D058407:Electroencephalography Phase Synchronization / Q000502:physiology*; D055724:Electrophysiological Phenomena / Q000502:physiology*; D018728:Entorhinal Cortex / Q000503:physiopathology*; D004827:Epilepsy / Q000139:chemically induced / Q000503:physiopathology*; D008297:Male; D066195:Piriform Cortex / Q000503:physiopathology*; D026902:Potassium Channel Blockers / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D026902:Potassium Channel Blockers; D015761:4-Aminopyridine
keywords: 4-aminopyridine; entorhinal cortex; epilepsy; high-frequency oscillations; piriform cortex