(441) GABAergic mechanism of sleep deprivation-induced seizure exacerbation in the Kv1.1-/- mouse model

Sleep deprivation (SD) is one of the most common triggers for breakthrough seizures among patients with epilepsy. However, the mechanisms underlying SD-induced seizure exacerbation are not understood. Here, we hypothesized that SD exacerbates seizures in part due to a reduction in GABAergic tonic inhibition (GTI) in the Kv1.1^-/- mouse model of epilepsy.

Methods:

Male and female Kv1.1^-/- mice underwent epidural EEG electrode implantation at ~P35 under isoflurane. Following a one to two day recovery, EEG recordings were done in the SD group (n=19) on a baseline day, during 5 days of SD (performed by presenting novel objects or gentle handling for four hours a day between ~7-11 am) and on a recovery day whereas it was done for seven days in controls (n=6) with no SD. A separate cohort of Kv1.1^-/- mice underwent same SD protocol (n=6) or no SD (n=6) after which they were sacrificed on the day of recovery and whole-cell patch-clamp electrophysiology was performed to record tonic inhibitory currents in the dentate gyrus, measured by bath application of 100 µM Bicuculline. Differences in mean seizure frequency across the days of recording in SD and controls was evaluated using repeated measures ANOVA. Mean tonic currents as well as miniature inhibitory postsynaptic potentials (mIPSCs) frequency and amplitude was compared between control and SD groups using Mann-Whitney U test.

Results: During the EEG recording in SD group, 9/19 survived all seven days and those that survived until day 4 of SD (n=14) were included in seizure analysis. During SD, 10/19 went into status epilepticus and all ten died. No mortality was seen among the controls. Mean daily seizure frequency (±SEM) between SD and controls across the seven days was 2.5±0.5 vs. 0.33±0.21 for day1; 3.5±1.11 vs. 1.66±0.49 for day 2; 8.21±2.51 vs. 1±0.51 on day 3; 10.92±2.36 vs. 1.5±0.56 on day 4; 10.42±2.27 vs. 1.33±0.49 on day 5; 6.777±1.36 vs. 2.83±1.60 on day 6 and 2.66±0.89 vs. 3.16±1.1 on day 7 (F(8, 48)=3.71; p< 0.001). Within the SD group, no difference was seen in seizure frequency between subjects (p=0.25). The mean tonic inhibitory current was 6.23±1.1 pA in control group (15 cells from 4 animals) whereas it was 3.43±1.1pA for SD group (13 cells from 4 animals) (p=0.06). No differences were seen between mean mIPSC frequency (1.7±0.2 vs. 1.9±0.2 Hz) or amplitude (48.3±3.2 vs. 43.8±4.4 pA) between control and SD groups. Further experiments are being done to increase the sample size and to extract tonic current data after three days of SD, near the peak time of the electrographic seizures.

Conclusions: SD exacerbated seizures acutely after SD in Kv1.1-/- mice, but it is likely that compensatory responses result in reduced seizures frequency after third SD day. SD also hastens mortality in this model. Electrophysiology data showed no change in tonic currents and synaptic release or concomitant reduction of extracellular GABA concentration by the recovery day. To understand further the link between reduced GTI and SD-induced seizure exacerbation, tonic current experiments are being performed immediately after the third day of SD.

Funding: Please list any funding that was received in support of this abstract.: This work was supported by NIH grant: 1 R21NS104612-01A1 (PI:Maganti); 1R21NS116546 (PI: Jones)
Click here to view image/table