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Optogenetic dissection of ictal propagation in the hippocampal-entorhinal cortex structures.

ABSTRACT: Temporal lobe epilepsy (TLE) is one of the most common drug-resistant forms of epilepsy in adults and usually originates in the hippocampal formations. However, both the network mechanisms that support the seizure spread and the exact directions of ictal propagation remain largely unknown. Here we report the dissection of ictal propagation in the hippocampal-entorhinal cortex (HP-EC) structures using optogenetic methods in multiple brain regions of a kainic acid-induced model of TLE in VGAT-ChR2 transgenic mice. We perform highly temporally precise cross-area analyses of epileptic neuronal networks and find a feed-forward propagation pathway of ictal discharges from the dentate gyrus/hilus (DGH) to the medial entorhinal cortex, instead of a re-entrant loop. We also demonstrate that activating DGH GABAergic interneurons can significantly inhibit the spread of ictal seizures and largely rescue behavioural deficits in kainate-exposed animals. These findings may shed light on future therapeutic treatments of TLE.

SUBMITTER: Lu Y

PROVIDER: S-EPMC4802168 | biostudies-literature | 2016 Mar

REPOSITORIES: biostudies-literature

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Optogenetic dissection of ictal propagation in the hippocampal-entorhinal cortex structures.

Lu Yi Y Zhong Cheng C Wang Lulu L Wei Pengfei P He Wei W Huang Kang K Zhang Yi Y Zhan Yang Y Feng Guoping G Wang Liping L

Nature communications 20160321

Temporal lobe epilepsy (TLE) is one of the most common drug-resistant forms of epilepsy in adults and usually originates in the hippocampal formations. However, both the network mechanisms that support the seizure spread and the exact directions of ictal propagation remain largely unknown. Here we report the dissection of ictal propagation in the hippocampal-entorhinal cortex (HP-EC) structures using optogenetic methods in multiple brain regions of a kainic acid-induced model of TLE in VGAT-ChR2 ...[more]

PMID: 26997093

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Project description:ObjectiveUsing MRI surface morphometry mapping, to evaluate local deformations of the hippocampus, parahippocampal gyrus, and entorhinal cortex in predicting conversion from mild cognitive impairment (MCI) to Alzheimer's disease (AD).MethodsBaseline brain MRI with surface morphological analysis was performed in 130 outpatients with MCI, broadly defined, and 61 healthy controls followed for an average of 4 years in a single site study.ResultsPatients with MCI differed from controls in several regions of the hippocampus and entorhinal cortex, and to a lesser extent in the parahippocampal gyrus. In the MCI sample, Cox regression models were conducted for time to conversion comparing converters to AD (n=31) and non-converters (n=99), controlling for age, sex and education. Converters showed greater atrophy in the head of the hippocampus, predominantly in the CA1 region and subiculum, and in the entorhinal cortex, especially in the anterior-inferior pole bilaterally. When distances of specific points representing localized inward deformation were entered together with the corresponding hippocampal or entorhinal cortex volume in the same Cox regression model, the distances remained highly significant whereas the volumes of the corresponding structures were either marginally significant or not significant. Inclusion of cognitive or memory measures or apolipoprotein E ?4 genotype as covariates, or restricting the sample to patients with amnestic MCI (24 converters and 81 non-converters) did not materially change the findings. In the 3-year follow-up sample of patients with MCI, logistic regression analyses using the same measures and covariates yielded similar results.InterpretationThese findings indicate selective early involvement of the CA1 and subiculum regions of the hippocampus and provide new information on early anterior pole involvement in the entorhinal cortex in incipient AD. Fine-grained surface morphometry of medial temporal lobe structures may be superior to volumetric assessment in predicting conversion to AD in patients clinically diagnosed with MCI.

Dataset Information

Optogenetic dissection of ictal propagation in the hippocampal-entorhinal cortex structures.

Publications

Optogenetic dissection of ictal propagation in the hippocampal-entorhinal cortex structures.

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