Mitochondrial dysfunction and ultrastructural damage in the hippocampus during kainic acid-induced status epilepticus in the rat.
OBJECTIVE
Prolonged and continuous epileptic seizure (status epilepticus) results in cellular changes that lead to neuronal damage. We investigated whether these cellular changes entail mitochondrial dysfunction and ultrastructural damage in the hippocampus, by using a kainic acid (KA)-induced experimental status epilepticus model.


METHODS
In Sprague-Dawley rats maintained under chloral hydrate anesthesia, KA (0.5 nmol) was microinjected unilaterally into the CA3 subfield of the hippocampus to induce seizure-like hippocampal EEG activity. The activity of key mitochondrial respiratory chain enzymes in the dentate gyrus (DG), or CA1 or CA3 subfield of the hippocampus was measured 30 or 180 min after application of KA. Ultrastructure of mitochondria in those three hippocampal subfields during KA-induced status epilepticus also was examined with electron microscopy.


RESULTS
Microinjection of KA into the CA3 subfield of the hippocampus elicited progressive build-up of seizure-like hippocampal EEG activity. Enzyme assay revealed significant depression of the activity of nicotinamide adenine dinucleotide cytochrome c reductase (marker for Complexes I+III) in the DG, or CA1 or CA3 subfields 180 min after KA-elicited temporal lobe status epilepticus. Conversely, the activities of succinate cytochrome c reductase (marker for Complexes II+III) and cytochrome c oxidase (marker for Complex IV) remained unaltered. Discernible mitochondrial ultrastructural damage, varying from swelling to disruption of membrane integrity, also was observed in the hippocampus 180 min after hippocampal application of KA.


CONCLUSIONS
Our results demonstrated that dysfunction of Complex I respiratory chain enzyme and mitochondrial ultrastructural damage in the hippocampus are associated with prolonged seizure during experimental temporal lobe status epilepticus.
Department of Neurology, E-Da Hospital and I-Shou University, Kaohsiung, Taiwan, Republic of China.
Yao-Chung
YC
Chuang
Alice Y W
AY
Chang
Jui-Wei
JW
Lin
Shih-Pin
SP
Hsu
Samuel H H
SH
Chan
D000818:Animals; D004195:Disease Models, Animal; D004569:Electroencephalography / Q000187:drug effects; D042967:Electron Transport Complex I / Q000187:drug effects / Q000378:metabolism; D014450:Electron Transport Complex III / Q000187:drug effects / Q000378:metabolism; D003576:Electron Transport Complex IV / Q000187:drug effects / Q000378:metabolism; D004833:Epilepsy, Temporal Lobe / Q000139:chemically induced / Q000201:enzymology / Q000378:metabolism; D006624:Hippocampus / Q000378:metabolism* / Q000648:ultrastructure*; D007608:Kainic Acid / Q000494:pharmacology; D008297:Male; D008928:Mitochondria / Q000378:metabolism / Q000648:ultrastructure*; D028361:Mitochondrial Diseases / Q000175:diagnosis / Q000201:enzymology / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism / Q000648:ultrastructure; D051381:Rats; D017207:Rats, Sprague-Dawley; D013226:Status Epilepticus / Q000139:chemically induced* / Q000201:enzymology / Q000378:metabolism*
D003576:Electron Transport Complex IV; D042967:Electron Transport Complex I; D014450:Electron Transport Complex III; D007608:Kainic Acid