Anticonvulsant action of 2,3-dihydroxy-6-nitro-7-sulfamoylbenzo(f)quinoxaline (NBQX), a competitive antagonist at non-N-methyl-D-aspartate receptors for excitatory amino acids, was studied in a model of cortical epileptic afterdischarges (ADs) in 12-, 18- and 25-day-old rat pups with implanted electrodes. Electrical stimulation of sensorimotor cortex was repeated four times with 20-min intervals, NBQX (in doses of 10, 30, 60 or 90 mg/kg i.p.) or solvent (dimethyl sulfoxide, 1 ml/kg i.p.) were injected 10 min after the first afterdischarge. Dimethyl sulfoxide did not change the phenomena recorded; NBQX shortened ADs or at least blocked progressive prolongation observed under control conditions. Intensity of movements accompanying stimulation decreased after NBQX, and clonic movements accompanying ADs were suppressed in a dose-dependent manner. The highest dose of NBQX disabled the animals; therefore, the action of this drug on motor skills was studied in another group of animals. Even the dose of 30 mg/kg NBQX interfered with motor performance in 12- and 18-day-old rat pups, 25-day-old rat pups were more resistant to this action. NBQX exhibited only moderate antiepileptic action (suppression of progressive lengthening of ADs) at doses where unwanted side effects were absent.

Institute of Physiology Academy of Sciences of the Czech Republic Prague