Various modifications of the intrahippocampal kainate model of mesial temporal lobe epilepsy in rats fail to resolve the marked rat-to-mouse differences in type and frequency of spontaneous seizures in this model.
Temporal lobe epilepsy (TLE) is the most common type of acquired epilepsy in adults. TLE can develop after diverse brain insults, including traumatic brain injury, infections, stroke, or prolonged status epilepticus (SE). Post-SE rodent models of TLE are widely used to understand mechanisms of epileptogenesis and develop treatments for epilepsy prevention. In this respect, the intrahippocampal kainate model of TLE in mice is of interest, because highly frequent spontaneous electrographic seizures develop in the kainate focus, allowing evaluation of both anti-seizure and anti-epileptogenic effects of novel drugs with only short EEG recording periods, which is not possible in any other model of TLE, including the intrahippocampal kainate model in rats. In the present study, we investigated whether the marked mouse-to-rat difference in occurrence and frequency of spontaneous seizures is due to a species difference or to technical variables, such as anesthesia during kainate injection, kainate dose, or location of kainate injection and EEG electrode in the hippocampus. When, as in the mouse model, anesthesia was used during kainate injection, only few rats developed epilepsy, although severity or duration of SE was not affected by isoflurane. In contrast, most rats developed epilepsy when kainate was injected without anesthesia. However, frequent electrographic seizures as observed in mice did not occur in rats, irrespective of location of kainate injection (CA1, CA3) or EEG recording electrode (CA1, CA3, dentate gyrus) or dose of kainate injected. These data indicate marked phenotypic differences between mice and rats in this model. Further studies should explore the mechanisms underlying this species difference.
Department of Pharmacology, Toxicology, and Pharmacy, University of Veterinary Medicine Hannover, Germany, and Center for Systems Neuroscience, Hannover, Germany.
Rebecca
R
Klee
Department of Pharmacology, Toxicology, and Pharmacy, University of Veterinary Medicine Hannover, Germany, and Center for Systems Neuroscience, Hannover, Germany.
Claudia
C
Brandt
Department of Pharmacology, Toxicology, and Pharmacy, University of Veterinary Medicine Hannover, Germany, and Center for Systems Neuroscience, Hannover, Germany.
Kathrin
K
Töllner
Department of Pharmacology, Toxicology, and Pharmacy, University of Veterinary Medicine Hannover, Germany, and Center for Systems Neuroscience, Hannover, Germany. Electronic address: wolfgang.loescher@tiho-hannover.de.
Wolfgang
W
Löscher
D000818:Animals; D004195:Disease Models, Animal; D004569:Electroencephalography; D004833:Epilepsy, Temporal Lobe / Q000139:chemically induced*; D006624:Hippocampus / Q000187:drug effects*; D007608:Kainic Acid; D008297:Male; D051379:Mice; D051381:Rats; D012640:Seizures / Q000139:chemically induced*; D013045:Species Specificity; D013226:Status Epilepticus / Q000139:chemically induced*
D007608:Kainic Acid
Anesthesia; EEG; Electrographic seizures; Hippocampus; Isoflurane; Kainic acid