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Effects of Circadian Regulation and Rest—Activity State on Spontaneous Seizures in a Rat Model of Limbic Epilepsy
Author(s) -
Quigg Mark,
Clayburn Hope,
Straume Martin,
Menaker Michael,
Bertram Edward H.
Publication year - 2000
Publication title -
epilepsia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.687
H-Index - 191
eISSN - 1528-1167
pISSN - 0013-9580
DOI - 10.1111/j.1528-1157.2000.tb00202.x
Subject(s) - circadian rhythm , status epilepticus , epilepsy , hippocampus , medicine , endocrinology , limbic system , rhythm , stimulation , temporal lobe , psychology , neuroscience , central nervous system
Summary:Purpose : Circadian regulation via the suprachiasmatic nuclei and rest–activity state may influence expression of limbic seizures. Methods : Male rats (n = 14) were made epileptic by electrical stimulation of the hippocampus, causing limbic status epilepticus and subsequent seizures. We monitored seizures with intrahippocampal electrodes in 12–12‐h light/dark (LD) cycles and in continuous dark (DD). We used radiotelemetry monitoring of activity to measure state and body temperature to determine circadian phase. Cosinor analysis and χ 2 tests determined whether seizures occurred rhythmically when plotted by phase. State was defined as inactive or active in 10‐min epochs based on whether activity count was below or above a cut‐off value validated from video observation. Results : In LD, the peak seizure occurrence was 14:59 h after circadian temperature peak (95% confidence limit, 13:37–16:19). Phasic seizure occurrence persisted in DD for 14:05 (12:31–15:38), p < 0.0001, against uniform mean distribution. In LD, 14,787 epochs contained 1,268 seizures; seizures preferentially occurred during inactive epochs (965 observed, 878 expected in proportion to the overall distribution of inactive versus active epochs; p < 0.001). In DD, 20,664 epochs contained 1,609 seizures; seizures had no preferential occurrence by state (999 observed, 1,025 expected; p = 0.16). Conclusions : Limbic seizures occurred with an endogenous circadian rhythm. Seizures preferentially struck during inactivity during entrainment to the light–dark cycle.