Anticonvulsant doses of ganaxolone do not compromise motor performance in immature rats

Neuroactive steroids that function as positive modulators of GABA-A receptors are potential anticonvulsant drugs. We previously demonstrated that ganaxolone is effective against pentetrazol-induced motor seizures in immature rats. In the present study, we examined the effects of ganaxolone in another model, cortical epileptic afterdischarges (ADs). The possible side effects of ganaxolone were studied in rats 12, 18, and 25 days of age following the implantation of epidural electrodes. Low-frequency stimulation of the sensorimotor cortical area elicited ADs characterized by a spike-and-wave rhythm and clonic seizures. Ganaxolone (5, 10, 20, or 40 mg/kg) was administered intraperitoneally after the first AD and stimulation was repeated five more times. The highest dose of ganaxolone (40 mg/kg) suppressed progressive prolongation of ADs in 25-day-old rats and postponed it in 12-day-old rats. No significant effect was observed in 18-day-old animals. Movements during stimulation and clonic seizures accompanying ADs were not affected by ganaxolone. Ganaxolone at doses of 20 and 40 mg/kg had no significant effect on motor function, such as surface righting, negative geotaxis, wire mesh ascending, and bar holding. After administration of 40 mg/kg ganaxolone to 18- and 25-day-old rats, spontaneous locomotion in the open field tended to decrease. Doses of ganaxolone with a moderate anticonvulsant effect in the present model did not seriously compromise motor performance.