Glycine potentiates the anticonvulsant action of diazepam and phenobarbital in kindled amygdaloid seizures of rats.

The effect of glycine on the anticonvulsant activity of diazepam and phenobarbital in fully developed kindled amygdaloid seizures in rats was determined. Glycine alone had no significant effect on the seizure response, either when administered orally 1 hr prior to the seizure test or when given chronically in a 0.5 M solution as the source of water. Administration of glycine (10 mmol/kg, oral) together with diazepam produced a significant reduction in both cortical epileptiform afterdischarge and the severity of seizures at doses of diazepam which had no significant effect on the seizures when administered alone. Glycine potentiated the effects of phenobarbital on the cortical afterdischarge but not the severity of the seizures. The observed potentiation of the effects of diazepam and phenobarbital suggests a glycinergic mechanism in the anticonvulsant action of these drugs which may be mediated in part by the inhibitory gamma-aminobutyric acid (GABA) systems.