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Received: 2010-08-30

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Crosschecked: 2011-08-09

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Journal of Zhejiang University SCIENCE B 2011 Vol.12 No.9 P.704-711


Changes of paired-pulse evoked responses during the development of epileptic activity in the hippocampus

Author(s):  Zhou-yan Feng, Xiao-jing Zheng, Cong Tian, Yang Wang, Hao-yu Xing

Affiliation(s):  Ministry of Education Key Lab of Biomedical Engineering, College of Biomedical Engineering & Instrument Science, Zhejiang University, Hangzhou 310027, China

Corresponding email(s):   hnfzy@yahoo.com.cn

Key Words:  Epilepsy, Paired-pulse depression, γ, -Aminobutyric acid (GABA), Picrotoxin (PTX), CA1 region, In-vivo

Zhou-yan Feng, Xiao-jing Zheng, Cong Tian, Yang Wang, Hao-yu Xing. Changes of paired-pulse evoked responses during the development of epileptic activity in the hippocampus[J]. Journal of Zhejiang University Science B, 2011, 12(9): 704-711.

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publisher="Zhejiang University Press & Springer",

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%T Changes of paired-pulse evoked responses during the development of epileptic activity in the hippocampus
%A Zhou-yan Feng
%A Xiao-jing Zheng
%A Cong Tian
%A Yang Wang
%A Hao-yu Xing
%J Journal of Zhejiang University SCIENCE B
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%I Zhejiang University Press & Springer
%DOI 10.1631/jzus.B1000316

T1 - Changes of paired-pulse evoked responses during the development of epileptic activity in the hippocampus
A1 - Zhou-yan Feng
A1 - Xiao-jing Zheng
A1 - Cong Tian
A1 - Yang Wang
A1 - Hao-yu Xing
J0 - Journal of Zhejiang University Science B
VL - 12
IS - 9
SP - 704
EP - 711
%@ 1673-1581
Y1 - 2011
PB - Zhejiang University Press & Springer
ER -
DOI - 10.1631/jzus.B1000316

Dysfunction of inhibitory synaptic transmission can destroy the balance between excitatory and inhibitory synaptic inputs in neurons, thereby inducing epileptic activity. The aim of the paper is to investigate the effects of successive excitatory inputs on the epileptic activity induced in the absence of inhibitions. Paired-pulse orthodromic and antidromic stimulations were used to test the changes in the evoked responses in the hippocampus. picrotoxin (PTX), γ;-Aminobutyric acid (GABA) type A (GABAA) receptor antagonist, was added to block the inhibitory synaptic transmission and to establish the epileptic model. Extracellular evoked population spike (PS) was recorded in the CA1 region of the hippocampus. The results showed that the application of PTX induced a biphasic change in the paired-pulse ratio of PS amplitude. A short latency increase of the second PS (PS2) was later followed by a reappearance of PS2 depression. This type of depression was observed in both orthodromic and antidromic paired-pulse responses, whereas the GABAergic PS2 depression [called paired-pulse depression (PPD)] during baseline recordings only appeared in orthodromic-evoked responses. In addition, the depression duration at approximately 100 ms was consistent with a relative silent period observed within spontaneous burst discharges induced by prolonged application of PTX. In conclusion, the neurons may ignore the excitatory inputs and intrinsically generate bursts during epileptic activity. The depolarization block could be the mechanisms underlying the PPD in the absence of GABAA inhibitions. The distinct neuronal responses to stimulations during different epileptic stages may implicate the different antiepileptic effects of electrical stimulation.

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