Developmental aspects of the pilocarpine model of epilepsy.

Prolonged seizures in young children may precede the later development of focal or generalized seizures. To study the age-related susceptibility to the development of chronic epilepsy we used the pilocarpine model of epilepsy (PME). This model is well characterized in adult rats, and presents three distinct periods: (a) an acute period of status epilepticus (SE), (b) a silent period of a progressive normalization of EEG and behavior, (c) a chronic period of spontaneous recurrent seizures. Wistar rats aged 7-120 days received pilocarpine hydrochloride (170-380 mg/kg, i.p., according to age), 30 min after methylscopolamine (1 mg/kg, s.c.). All surviving animals were observed for 120 days. The results indicate that chronic seizures following pilocarpine-induced status epilepticus can be induced in rats if the status is induced after the 18th day of life. The age-related differences in the susceptibility of young rats to developed chronic epilepsy reflect the complexity of seizure activity in immature brain and provide for an apparent distinction between the mechanisms of epileptogenesis in the mature and developing nervous system.