Abstracts

Rationale: The National Institute of Neurological Disorders and Stroke (NINDS) Epilepsy Therapy Screening Program’s (ETSP) contract site at the University of Utah seeks to facilitate the discovery of treatments for drug-resistant epilepsy using mouse models to screen investigational compounds. There may be instances when different strains of animals are needed (due to availability, reproducibility, or other causes), and determining the similarity and differences in pharmacology of ASDs between strains is essential. Since, the protective response to ASDs has been shown to be influenced by mouse strains (Frankel, Taylor et al. 2001, Leclercq and Kaminski 2015), we investigated the effects of a battery of well characterized ASDs in commonly used strains of mice.

Methods: We determined the seizure threshold in the Maximal Electroshock (MES) and 6 Hz 44 mA tests for several strains of male mice (CF-1 from Envigo, CF-1, CD-1 and C57Bl/6J from Charles River). Then we determined the median effective dose (ED₅₀) of five prototype ASDs: sodium valproate (VPA), levetiracetam (LEV), phenytoin (PHT), ezogabine (EZG), and clobazam (CLB), in MES and 6 Hz test for each strain. The data obtained was compared to historical data obtained from laboratory notebooks since 1975 and the ETSP Database at NINDS/NIH. This comparison also allowed us to investigate changes in experimental results from the CF-1 strain from Charles River over a long period of time.

Results: The MES seizure threshold is significantly lower for the CF-1 mice from Charles River than for the CF-1 from Envigo, the CD-1 and the C57Bl/6J. In 6 Hz, there was no statistical difference between the seizure threshold of the different strains. For most of the prototype ASDs, there were statistical differences in pharmacology between the mouse strains. The most surprising difference was the response to LEV in the 6 Hz model between CF-1 mice obtained from Charles River and those obtained from Envigo, wherein LEV was more than 5 times more potent in the Envigo mice. When looking at the historical data for CF-1 mice obtained from Charles River, there was a statistical difference between the Convulsive Current eliciting seizures in 97% of animals (CC₉₇) obtained in MES, but that had no impact on the ED₅₀ determined for the prototype ASDs. While no difference was observed in 6 Hz seizure threshold in the historical data, noticeable differences occur for EZG, CLB, and PHT that will be further investigated.

Conclusions: This analysis was essential to determine if there were any significant differences in either seizure thresholds or responses to a battery of commonly used ASDs in either different strains of mice or the same strain over a period of time. Rigor and reproducibility are essential for a screening program and this investigation suggests that strain dependent and animal supplier differences could influence experimental results.

Funding: Please list any funding that was received in support of this abstract.: This project has been funded by Federal funds from the National Institute of Neurological Disorders and Stroke, Epilepsy Therapy Screening Program, National Institutes of Health and Department of Health and Human Services, under Contract No. HHSN271201600048C.