Feline amygdaloid kindling and sleep

Six hourly polygraphic examinations of sleep organization were made before and after amygdaloid (AM) kindling in 7 cats. After completion of AM kindling and the repetitive induction of kindled convulsion, the percentage of time spent in rapid eye movement sleep (REMS) significantly decreased, although the animals began to spend significantly more time in sleep. This altered sleep pattern persisted during an extended 22.5 h recording in 2 cats. The decreased waking (W) and REMS, as well as the increased slow wave sleep (SWS), appeared to be due to changes in mean duration but not in the total number of periods. Suppression of REMS but not SWS was also manifested as a delayed onset of REMS following sleep onset, the latency of which remained constant upon placement of animals in the recording chamber. These changes in sleep organization were transient, however, as they returned completely to the baseline pre-kindling level after a rest interval of 3-4 weeks without kindling stimulation. It is concluded that sleep organization changes, particularly those characterized by the suppression of REMS, are independent of the acquisition of AM-kindled seizure susceptibility; rather they are the direct correlates of generalized convulsion itself.