Damage, reorganization, and abnormal neocortical hyperexcitability in the pilocarpine model of temporal lobe epilepsy

Damage, reorganization, and abnormal neocortical hyperexcitability in the pilocarpine model of temporal lobe epilepsy

Author Sanabria, Emilio Rafael Garrido Autor UNIFESP Google Scholar
Silva, Alexandre Valotta da Autor UNIFESP Google Scholar
Spreafico, R. Google Scholar
Cavalheiro, Esper Abrão Autor UNIFESP Google Scholar
Institution Universidade Federal de São Paulo (UNIFESP)
Ist Nazl Neurol C Besta
Abstract Purpose: Clinical, neuropathological, and electro-physiological data have shown that limbic structures are involved in the pathogenesis of temporal lobe epilepsy (TLE). in most cases, limbic-originated seizures frequently spread to extrahippocampal areas. It is unclear whether such distant circuitries, especially the neocortex, exhibit abnormal electrophysiology as consequences of a chronic epileptogenic process. the present research studied neuropathological abnormalities and in vitro electrophysiological properties of sensorimotor neocortex in pilocarpine-treated epileptic rats.Methods: Adult epileptic animals showing six to seven seizures/week and saline-injected rats were selected for neurohistology. Coronal sections were sampled throughout the anteroposterior extent of the diencephalon and stained with cresyl violet (Nissl). Immunocytochemistry (ICC) was performed using anti-neurofilament (SMI-311) antibody. Extracellular (layer II/III) and intracellular (layer V) recordings were per-formed in coronal sensorimotor neocortical slices. Several electrophysiological aspects were examined such as evoked responses, intrinsic properties, and firing patterns of layer V pyramidal cells.Results: Niss1 staining showed a significant decrease of cortical thickness in epileptic rats when compared with controls, particularly in superficial layers (II-IV). Such abnormalities were also revealed by SMI-311 staining. SMI-311-labeled dendrite arborizations were more complex in layers I-II of epileptic rats. Epileptic rats manifested several abnormalities in extracellular field responses including hyperresponsiveness and presence of alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionate (AMPA)-mediated polysynaptic activity. Although no significant changes were observed concerning passive intrinsic properties, it was possible to detect a higher proportion of bursting neurons distributed in layer V (60%) of epileptic rats compared with 22% in control slices.Conclusions: Taken together, our findings indicate damage, reorganization, and chronic hyperexcitability of sensorimotor neocortex in experimental TLE.
Keywords neocortex
epilepsy
pilocarpine
immunocytochemistry
burst
Language English
Date 2002-01-01
Published in Epilepsia. Malden: Blackwell Publishing Inc, v. 43, p. 96-106, 2002.
ISSN 0013-9580 (Sherpa/Romeo, impact factor)
Publisher Blackwell Publishing Inc
Extent 96-106
Origin http://dx.doi.org/10.1046/j.1528-1157.43.s.5.31.x
Access rights Open access Open Access
Type Article
Web of Science ID WOS:000177445900018
URI http://repositorio.unifesp.br/handle/11600/26683

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