Intra-Hippocampal Kainate Model (mouse)
The intra-hippocampal kainate mouse model of mesial temporal lobe epilepsy (MTLE) recapitulates many of the characteristics observed in human patients with temporal lobe epilepsy. The MTLE mouse is characterized by an initial neurotoxic event, a unilateral intrahippocampal injection of kainic acid (KA) into the dorsal hippocampus, which induces a non-convulsive status epilepticus (SE) lasting several hours. This initial event is followed by a period of two to three weeks during which the appearance of spikes, bursts, and discharges occurs. Spontaneous, recurrent, electrographic hippocampal paroxysmal discharges (HPD) are afterwards stably observed in the injected hippocampus and stereotyped for the whole life of the animal (Bouilleret et al., 1999; Riban et al., 2002; Duveau et al., 2016, Duveau and Roucard, 2017; Twele et al., 2017). These HPDs occur spontaneously about 30-60 times per hour when the animals are in a state of quiet wakefulness, generally last 15-20 sec, and are associated with behavioral arrest and/or mild motor automatisms. To reliably record HPDs, the animals need to be implanted with an intra-hippocampal depth electrode.
To induce SE (precipitating event), male C57BL/6J mice of at least 10 weeks of age will be injected 1 nmol KA solution (Sigma) in 0.9% sterile saline into the right dorsal hippocampus under isoflurane anesthesia (Duveau et al., 2016). After KA injection, all mice will be implanted with a bipolar electrode into the injected hippocampus. Before and between 6 and 8h after surgery, animals will receive an injection of buprenorphine (0.05mg/kg). After surgery, mice will be housed in individual cages with food and water ad libitum and kept under a 12/12h light-dark controlled cycle. All experiments will be performed during the light hours of the cycle. To detect and quantify electrographic HPDs, the electroencephalogram (EEG) will be recorded in freely moving animals placed in individual plexiglass cages using SystemPlus Evolution (Micromed). Offline analysis will be performed by an expert to detect HPDs, defined as rhythmic high-amplitude sharp waves occurring with a frequency of 5-10 Hz and lasting at least 5 seconds with a minimum interevent interval of 1 second.
To evaluate the efficacy of a test drug/therapy to prevent development of epilepsy, the treatment will be initiated after the induction of SE (precipitating event) and before the appearance of spontaneous, recurrent, electrographic HPDs. The primary outcomes measured once the treatment is terminated will be occurrence/absence of HPDs, but the effect on severity (frequency and duration) of HPDs, and sensitivity of HPDs to drugs that failed to treat it in prior trials may also be examined. To determine the efficacy of a test drug/therapy to modify the disease, the treatment will be initiated after the appearance of spontaneous, recurrent, electrographic HPDs and the outcomes measured following washout period will be the same as described above for the disease prevention paradigm. The exact treatment regimen (the time of the initiation and frequency and duration of the treatment) will be based on various factors such as the effective dose identified in prior studies, pharmacokinetics and mechanism of action, and may vary between the treatments.