Hyperthermia‐induced seizure experiments were conducted in Scn1a+/− mice at age postnatal day 14‐16 (P14‐16) using a rodent temperature regulator (TCAT‐2DF, Physitemp Instruments, Inc, Clifton, NJ) reconfigured with a Partlow 1160 + controller (West Control Solutions, Brighton, UK) connected to a heat lamp and RET‐3 rectal temperature probe. Fifteen minutes prior to the target experimental (post‐dose) time point for each drug, the rectal probe was inserted. Mice acclimated to the temperature probe for 5 min before the hyperthermia protocol was started. Mouse core body temperature was elevated 0.5°C every 2 min until the onset of the first clonic convulsion with loss of posture or until 42.5°C was reached. Mice that reached 42.5°C were held at temperature for 3 min. If no seizure occurred during the hold period, the mouse was considered seizure‐free. After thermal induction procedure, plasma samples were isolated as described above and stored at −80°C until assayed. Threshold temperatures were compared using the time to event analysis (logrank Mantel‐Cox), and P < 0.05 was considered statistically significant. No significant sex differences were observed, so groups were collapsed across sex.
Experimental time points were based on previously determined time‐to‐peak plasma and brain concentrations or effect from the literature or our pharmacokinetic studies. Experimental time points used were as follows: 40 min‐ levetiracetam; 45 min‐ carbamazepine, lamotrigine, phenobarbital; 90 min‐ stiripentol, clobazam, topiramate; 120 min phenytoin.20 , 21 , 22 , 23 , 24 Valproic acid was administered after the 5 min acclimation period.25 , 26 Matched vehicle controls were run for each experimental time point. Vehicle A (saline) was administered at 0, 40, 45, and 90 min. No statistical difference was identified between the four time points and all vehicle A‐treated mice were combined into one group. Vehicles B (0.5% methylcellulose), C (5% hydroxypropyl‐β‐cyclodextrin), and D (vegetable oil) were administered at 120, 45, and 90 min, respectively.
Experimental time points were based on previously determined time‐to‐peak plasma and brain concentrations or effect from the literature or our pharmacokinetic studies. Experimental time points used were as follows: 40 min‐ levetiracetam; 45 min‐ carbamazepine, lamotrigine, phenobarbital; 90 min‐ stiripentol, clobazam, topiramate; 120 min phenytoin.
