Sleep-wakefulness alterations in amygdala-kindled rats

Our aim was to study the relation between epilepsy and sleep-wakefulness cycles in the amygdala-kindling model of temporal lobe epilepsy.

Adult male Wistar rats were electrically kindled through bipolar electrodes implanted in the anterior amygdala. Polysomnographic recordings were taken before and after kindled seizures for 6 h. For the studies on the effects of a single, full-blown seizure, recordings were taken immediately after the seizure and daily thereafter until the recordings returned to baseline values. For studies on the effects of five full-blown seizures, recordings were taken immediately after the fifth seizure and then on day 1, 2, 3, 5, 7, 14, 21, and 28.

Polysomnographic recordings taken immediately after the first full-blown seizure revealed an initial increase in the duration of deep slow-wave sleep (SII), a decrease in the light slow-wave sleep (SI) stage of non-rapid eye movement (NREM) sleep, and a decrease in the quiet wakefulness (W2) stage of wakefulness. All these parameters returned to baseline values after 24 h. The duration of rapid eye movement (REM) sleep increased and returned to the baseline value after 48 h. Five consecutive full-blown seizures caused an increase in the duration of SII from the day the seizures occured until day 28, whereas the duration of SI decreased for 72 h. The duration of REM sleep, decreased only on the day of the seizures and day 1, while decreases in the number of REM episodes were observed on the day of the seizure, day 2 and day 14.

Our study indicates that even a single, full-blown seizure can cause alterations in the architecture of sleep-wakefulness cycles for a short duration, and that multiple seizures produce long-term effects.