Epilepsy Models in Rats and Mice
Epilepsy is not fully controlled although many therapies with diverse mechanisms have been developed.1,2 Epilepsy affects a minimum of 3 million adults and almost 500,000 children in the US alone.3 The clinical value of valium-based modulators of epilepsy is seen in that some of them have been marketed for over 50 years.4 However, these drugs, despite their efficacy, have issues with abuse/dependency liabilities and impairment of either brain function and/or muscle coordination.5 Retaining the efficacy of these drugs, but reducing the risk of using them has been the goal of epilepsy research for over 4 decades,6,7 but the goal has not been reached.
Induction:
Male rats will be ordered to be at least 90-100g and at least ~28 days old when on study, and male mice will be ordered to be at least 21-32g and at least 5-12 weeks old when on study.4 Developmental studies of infantile seizures will use all rat pups resulting from timed-pregnant animals, and the pups may be tested between postnatal days 7-70.8-12 Some clients may prefer a developmental model of infantile spasms (e.g. West syndrome) that involves treating the dams with betamethasone (0.4 mg/kg i.p) or restraint stress (5-45 minutes) delivered twice on gestational day 15.13-17 A graphical representation of a typical study design is below and would apply to any age of rat. Study designs for mice are similar except the post-induction monitoring period would only be 30 minutes.
Control and Test articles will be administered prior to seizure induction. Control arms include vehicle controls that match the longest timing of the test articles, allopregnanolone (5 mg/kg SC) at 90, 30, and 15 minutes before seizure induction (separate arms for each time point), and diazepam (10 mg/kg, IP) 30 minutes prior to seizure induction.4,18 Some developmental studies may use up to 3 doses of adrenocorticotrophic hormone (ACTH; 0.1-0.4 mg/kg i.p.) as another control arm.13-17
Seizures will be induced at study time 0 by the administration of one of 4 exogenous stimuli: pentylenetetrazol SC or IP (30 mg/kg mice; 10-40 mg/kg rats),4,9-11 kainic acid IP (30 mg/kg mice; 5-30 mg/kg rats),8 N-methyl-D-aspartate (5-200 mg/kg IP depending on age),13-17 or two, 2-minute pulses of 140dB noise (fire alarm or similar placed with the animal in a sound-attenuating box; 1-minute intertrial interval).12 The animals will then be evaluated in the following tests outlined below (N=10 for each arm):
Disease Parameters & Clinical Assessment:
- Rotarod – SOP 60.01, animals, if physically mature enough (at least postnatal day 23), may be trained on study days -2 and -1 and assessed 5 minutes prior to seizure induction on study day 0.
- Modified Racine Scoring – observation/video recording of all animals for 30 minutes (mice) or 30-60 minutes (rat) after seizure induction. Scoring is as follows:
- No Change
- Loss of Motion
- Facial Jerking
- Neck Jerking
- Clonic convulsion while sitting
- Any convulsions while on belly and/or Pure Tonic convulsion
- Any convulsions/tonic/clonic that occur while animal lays on its side and/or Wild Jumping19
- Barnes Maze – SOP 64.01, animals, if physically mature enough (at least postnatal day 28), may be baselined prior to seizure induction on study day 0 and then tested again as late as postnatal day 70.
- Morris Water Maze – SOP 66.01, animals, if physically mature enough (at least postnatal day 38), may be baselined prior to seizure induction on study day 0 and then tested again as late as postnatal day 70.
Histopathological Assessment:
as requested by client; neuroprotection (H&E or neuron-specific IHC) and neuronal sprouting (Timm silver stain) in hippocampus.
Sample Data (Click on image to enlarge):
