Abstracts

Rationale: Circadian rhythms are primarily controlled via expression and interplay of CLOCK genes in the suprachiasmatic nucleus (SCN), though modulated by environmental cues and can sustain under constant conditions. Circadian rhythms are known to be abnormal in the epileptic state. Here, we assess the circadian rest-activity patterns, circadian distribution of seizures and clock gene oscillations under diurnal and constant conditions in an animal model of epilepsy. Methods: Actigraphy, which measures rest-activity patterns, was examined under diurnal (12-12, light-dark) (LD) or constant dark conditions (DD) over several days in Kcna-1 null mutant mice (KO) and wild type (WT) controls. Mice were housed individually in 6" diameter cages with food and water provided ad libitum and actigraphy monitor suspended at the top of the cage. Activity counts were sorted into 1-minute bins and plotted across 24-hours. Chi-squared periodogram analysis was performed with the peak correlations averaged across cohorts and compared between groups. Following actigraphy, animals were sacrificed, hypothalamic area was dissected and clock genes were examined at different zeitgeber times (ZT0; ZT6; ZT12 and ZT18) using RT-PCR techniques. Additionally, circadian distribution of seizures was examined across 24hrs under diurnal and constant conditions in a separate group of KO and WT controls. Results: Circadian rest-activity patterns are markedly disrupted in KO under both diurnal and constant conditions compared to WT controls which had more activity counts during nighttime (awake) and much less activity counts during daytime (sleep). Furthermore, the circadian period was markedly prolonged in epileptic KO mice under both diurnal (n=9, 29.38 ± 1.74 hrs) and constant conditions (n=9, 27.26 ± 1.62) compared to WT controls under either diurnal conditions or constant darkness (WT-LD n=6, 23.71 ± 0.13 hours; WT-DD animals n=20, 23.68 ± 0.15 hours) which were statistically significant [LD: F(8, 5)=261.8; p<0.0001; DD: F(8, 19)=50.61; p<0.0001]. Seizures had a circadian pattern with peak of seizures occurring at ZT 8 under diurnal conditions. Clock genes oscillations across the 24hrs will be reported between the groups under LD and DD conditions. Conclusions: Circadian rhythms are markedly disrupted in epileptic KO mice, especially with markedly prolonged circadian period compared to WT controls under both diurnal and constant conditions. Further analysis and studies need to be performed to examine whether this is a function of seizure occurrence versus aberrant oscillation of clock genes.