GABA-B receptor antagonist CGP 35348 interferes with an arrest of cortical epileptic afterdischarges in developing rats.

Epileptic seizures activate not only excitatory but also inhibitory systems what results in an arrest of seizures. Our recent data indicate that GABAergic inhibition plays an important role in this process in cortically elicited seizures. We started to study the role of GABA-B receptors in cortical epileptic afterdischarges (ADs) in immature rats 12, 18 and 25 days old with implanted electrodes. Low-frequency stimulation of sensorimotor cortical area was repeated with increasing intensities of stimulation current. Thresholds for movements directly elicited by stimulation, for spike-and-wave type of AD, for clonic seizures accompanying this type of ADs and for transition into limbic type of AD were decreased by the 200mg/kg dose of a GABA-B receptor antagonist CGP35348 in all three age groups. Duration of ADs was markedly increased by 50, 100 as well as 200mg/kg dose of CGP35348. The effects were best expressed in 18-day-old rats. To conclude, GABA-B receptors play an important role in generation and especially in arrest of cortical seizures in immature rats.