6 Hz Electrical Stimulation Test (mouse, rat)

The 6 Hz test is a model of focal seizures that shows resistance to a number of the current antiseizure drugs. The seizures are induced by a low-frequency (6 Hz, 0.2 msec rectangular pulse), long-duration (3 sec), 44 mA current (2 times the convulsive current producing seizures in 97% of animals - CC97) or 32 mA delivered through corneal electrodes (Barton et al., 2001). A drop of 0.5% tetracaine hydrochloride in 0.9% saline (anesthetic/electrolyte) solution is applied to the eyes of all animals prior to the placement of corneal electrodes. The seizure in mice is characterized by an initial momentary stun followed immediately by jaw clonus, forelimb clonus, twitching of the vibrissae, and Straub tail. The seizure in rats include head nodding, jaw clonus, forelimb clonus with occasional bilateral forelimb clonus, rearing, and loss of the righting reflex (Metcalf et al., 2017). Animals not displaying this behavior within the one-minute observation period are considered “protected”.

Initial qualitative screen for anticonvulsant activity in the 6 Hz seizure model is performed with N = 4 male CF-1 mice or Sprague-Dawley CD albino rats/dose/time point. Three doses and two timepoints based on supporting data are selected to examine the efficacy of the test compound. Quantification of the effective dose that confers protection in 50% of animals treated with the compound (ED50) is conducted at the time of peak effect (TPE) and is described separately.