Epileptogenesis in immature rats following recurrent status epilepticus.

Strong evidences link status epilepticus (SE) in childhood with the later development of epilepsy. Pilocarpine-induced SE in developing rats leads to late appearance of spontaneous epileptic seizures only when SE is induced after the 18th day of life. We examined the possibility that 3 consecutive episodes of pilocarpine-induced SE on postnatal days 7, 8 and 9 could induce behavioral, electrographic and histological epileptic changes in adult life. The animals also underwent behavioral tests (inhibitory step-down avoidance, skinner box, rota-rod, open field and elevated plus-maze). EEG recordings made at the age of 30, 60 and 90 days showed the occurrence of several episodes of spikes and/or polyspikes appearing simultaneously in hippocampus and cortex. Only three isolated spontaneous seizures were observed during the whole period of observation (120 days). The long-term effects of three consecutive episodes of SE include increased spontaneous exploratory activity, learning impairment, and reduced anxiety when tested on P60. Our findings provide evidence for EEG changes and cognitive deficits in adult life following recurrent SE on postnatal days 7-9.

Effect of physical exercise on seizure occurrence in a model of temporal lobe epilepsy in rats.

Although the favorable effect of physical fitness on general health is unquestionable, physical exercise and fitness programs in patients with epilepsy are still a matter of controversy. Little objective evidence regarding the effect of exercise on seizure frequency and severity has been reported. One sought to clarify the relationship between exercise and epilepsy in an animal model of temporal lobe epilepsy (the pilocarpine model of epilepsy). To evaluate the effect of an aerobic physical program on seizure frequency, 29 epileptic animals were continuously monitored during 24 h for 135 days after the first spontaneous recurrent seizure (SRS) and divided into three groups. The first group (N = 14) was submitted to an aerobic exercise program (training group). The second group (N = 7) was maintained in the treadmill for the same time as the training group without being submitted to physical exercise (sham group). The third group (N = 8) served as control. The behavioral observation was divided in three periods of 45 days. The first period was used to determine the number of seizures before physical training program. The second period was utilized to determine the number of seizures during the physical training program. The third period was used to analyze the frequency of seizures after the physical training program. The mean frequency of seizures in the control and sham groups increased significantly from period 1 to period 2 and from period 1 to period 3. However, in the training group, the frequency of seizures did not change significantly between the three periods of 45 days of observation. When the same periods of the three groups were analyzed together, a significant reduction in seizure frequency was observed comparing the training group with the control and sham groups during the period of physical training. The data presented in this study suggest that physical exercise is not a seizure-inducing factor in this experimental model of epilepsy.

Ouabain induces apoptosis on PHA-activated lymphocytes.

Apoptotic cell death plays a critical role in immune system homeostasis, and c-myc protooncogene deregulated expression is a component of this programmed genomic response. Pharmacological intervention and modulation of peripheral lymphocytes apoptosis would have important implications. The present results indicate that ouabain, a specific inhibitor of Na+K(+)-ATPase, promotes an increased expression of c-myc mRNA, and induces apoptosis in PHA-stimulated lymphocytes. Furthermore, this ouabain-induced apoptosis cannot be counteracted by the addition of exogenous IL-2.

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.