Diurnal variation in pilocarpine-induced generalized tonic-clonic seizure activity

The efficacy of the cholinergic agonist pilocarpine to evoke generalized se izures in rats was examined over the 24-h photocycle. Both seizure latency and severity during the 24-h period exhibited marked diurnal variation. Sei zure activity generalized more rapidly throughout the dark phase and was of ten characterized by wild running clonus and tonic extensor convulsions. In contrast, electrographic seizures during the light phase were mainly assoc iated with facial/forelimb clonus and rearing typical of pilocarpine-induce d seizures. These data su est that the sensitivity of the rodent brain to p ilocarpine exhibits day-night variation and seizure activity induced during the dark phase may generalize via the brainstem. (C) 2001 Elsevier Science B.V. All rights reserved.