TY - JOUR
T1 - A novel focal seizure pattern generated in superficial layers of the olfactory cortex
AU - Uva, Laura
AU - Saccucci, Stefania
AU - Chikhladze, Maia
AU - Tassi, Laura
AU - Gnatkovsky, Vadym
AU - Milesi, Gloria
AU - Morbin, Michela
AU - de Curtis, Marco
PY - 2017/3/29
Y1 - 2017/3/29
N2 - © 2017 the authors. Seizure patterns identified in focal epilepsies caused by diverse etiologies are likely due to different pathogenic mechanisms. We describe here a novel, region-specific focal seizure pattern that mimics seizure activity observed in a subpopulation of patients submitted to presurgical monitoring with intracerebral electrodes. Distinctive seizure-like events (SLEs) are induced in the olfactory regions by acute treatment of both tangential brain slices and the isolated guinea pig brain with the potassium channel blocker 4-aminopyridine. Analysis of field potentials, intracellular activities, and extracellular potassium changes demonstrates that SLEs in the piriform cortex initiate in the superficial layer 1 lacking principal neurons with an activity-dependent increase of extracellular potassium. SLE progression (but not onset) does not require the participation of synaptic transmission and is mediated by diffusion of potassium to deep cortical layers. The novel seizure pattern here described is not observed in other cortical regions; it is proposed to rely on the peculiar organization of the superficial piriform cortex layers, which are characterized by unmyelinated axons and perisynaptic astroglial envelopes. This study reveals a sequence of ictogenic events in the olfactory cortex that were never described before in other cortical structures and supports the notion that altered potassium homeostasis and unmyelinated fibers may represent a potential vehicle for focal ictogenesis.
AB - © 2017 the authors. Seizure patterns identified in focal epilepsies caused by diverse etiologies are likely due to different pathogenic mechanisms. We describe here a novel, region-specific focal seizure pattern that mimics seizure activity observed in a subpopulation of patients submitted to presurgical monitoring with intracerebral electrodes. Distinctive seizure-like events (SLEs) are induced in the olfactory regions by acute treatment of both tangential brain slices and the isolated guinea pig brain with the potassium channel blocker 4-aminopyridine. Analysis of field potentials, intracellular activities, and extracellular potassium changes demonstrates that SLEs in the piriform cortex initiate in the superficial layer 1 lacking principal neurons with an activity-dependent increase of extracellular potassium. SLE progression (but not onset) does not require the participation of synaptic transmission and is mediated by diffusion of potassium to deep cortical layers. The novel seizure pattern here described is not observed in other cortical regions; it is proposed to rely on the peculiar organization of the superficial piriform cortex layers, which are characterized by unmyelinated axons and perisynaptic astroglial envelopes. This study reveals a sequence of ictogenic events in the olfactory cortex that were never described before in other cortical structures and supports the notion that altered potassium homeostasis and unmyelinated fibers may represent a potential vehicle for focal ictogenesis.
KW - 4-aminopyridine
KW - Extracellular potassium
KW - Human intracerebral EEG recordings
KW - In vitro guinea pig brain
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UR - http://www.scopus.com/inward/citedby.url?scp=85016497011&partnerID=8YFLogxK
U2 - 10.1523/JNEUROSCI.2239-16.2016
DO - 10.1523/JNEUROSCI.2239-16.2016
M3 - Article
C2 - 28264979
AN - SCOPUS:85016497011
VL - 37
SP - 3544
EP - 3554
JO - Journal of Neuroscience
JF - Journal of Neuroscience
SN - 0270-6474
IS - 13
ER -