Altered Circadian Rhythms and Clock Genes in Epileptic Mouse Model (S26.003)

Abstract

Objective: To examine circadian rhythm and the expression of genes associated with circadian rhythms extracted from hypothalamus in epileptic Kcna-1 null mouse model.

Background In animal models of limbic epilepsy, seizures tend to occur with a circadian rhythm, even under constant conditions. Other studies showed that circadian rhythms are disrupted due to the epileptic condition, but the physiological basis of circadian distribution of seizures and disrupted circadian rhythm is not understood.

Design/Methods: Circadian rest-activity patterns were measured in epileptic Kcna-1 knockouts using actigraphy over a 4 day period, compared to wild type mice. Hypothalamic areas was isolated from both groups at 4 different Zeitgeber times (ZT: 0, 6, 12 and 18 hrs) under normal light or infrared light and rapidly frozen at -60ºC. Standard RT-PCR technique with 4 clock gene primers such as Per1, Per 2, CLOCK and Bmal was employed. Differences in circadian rest-activity patterns were evaluated between epileptic and wild type mice using cosinor analysis. Differences in clock gene expression was analyzed using one-way ANOVA.

Results: Circadian rest-activity patterns of Kcna-1 knockouts were significantly disrupted compared to wild type mice. The circadian locomotor activity count was much higher during lights-off and much lower during lights-on for wild type mice where as locomotor activity counts were much higher both during lights-on and lights-off for epileptic mice. RT-PCR analysis showed that Per 1 and CLOCK expression was high in the early subjective night where as expression of Bmal was high in the early subjective day for epileptic mice where as Per 1, CLOCK and Bmal peaked at midnight for wild type mice.

Conclusions: Circadian rhythms of rest-activity periods are disrupted in epileptic mice which may have a genetic basis. It also remains to be seen whether circadian distribution of seizures is due to altered expression of clock genes.

Supported by: Arizona Biomedical Research Commission Grant.

Disclosure: Dr. Maganti has received personal compensation for activities with UCB Pharma, GlaxoSmithKline, Inc., Cyberonics, Lundbeck Research USA, Inc., Arizona Biomedical Research Commission, Barrow Neurological Foundation as a speaker, consultant and/or grant support staff. Dr. Wallace has nothing to disclose. Dr. Kim has nothing to disclose.