Kainic acid-induced limbic seizures in cats: some reflections on sleep-epilepsy interactions

Sleep-epilepsy interactions were investigated in a model of temporal lobe seizures induced in cats by intra-amygdaloid kainic acid (KA) microinjections. We found that limbic status epilepticus disrupted sleep for 2 or 3 days after injection. Sleep, in turn, modulated the frequency of interictal discharges. However, such modulation was variable depending on the time elapsed since KA injection. For this and other reasons (such as the occurrence of subclinical seizures during paradoxical sleep), we postulate a dual effect--facilitatory or inhibitory--of paradoxical sleep on limbic epilepsy. A role in seizure induction for bulbopontine structures is proposed on the basis of seizure precipitation during phasic paradoxical sleep. Propagated limbic seizures and paradoxical sleep without atonia displayed similar behavioral patterns. This fact and the possibility that a seizure may substitute for paradoxical sleep, lead us to think that limbic seizures and paradoxical sleep subserve similar functions. One of them might be the elimination of a potentially neurotoxic endogenous product.