L-Deprenyl (selegiline) is an irreversible inhibitor of monoamine oxidase type B, but also exerts several effects on dopamine and noradrenaline systems independent of monoamine oxidase type B inhibition. Thanks to these properties, L-deprenyl has gained wide acceptance in the therapy of Parkinson's disease by using L-deprenyl both with levodopa and alone. Furthermore, L-deprenyl improves the performance of patients with Alzheimer's disease. Epilepsy, particularly temporal lobe epilepsy with complex-partial seizures, is often associated with disturbances of cognitive function and behavior, and it has been suggested that a drug combining cognition-enhancing and antiepileptic activity would be of benefit in the treatment of epileptic patients. This prompted us to study if L-deprenyl exerts anticonvulsant efficacy in amygdala-kindled rats, i.e., a useful model of complex-partial seizures in humans. In addition to anticonvulsant activity, i.e., effects on already developed seizures, we determined whether L-deprenyl exhibits antiepileptogenic properties, i.e., suppressive effects on development of kindling. In all experiments, behavioral alterations of the rats in response to L-deprenyl were monitored closely. In order to assess the role of active metabolites in the anticonvulsant and behavioral effects of L-deprenyl in the kindling model, the D-enantiomer of deprenyl, which is metabolized to more potent compounds (D-amphetamine and D-methamphetamine) than the L-enantiomer, was used for comparison. In fully kindled rats, L-deprenyl potently increased the threshold for focal afterdischarges. The most marked increase in afterdischarge threshold (up to 250% above control) was seen after a dose of 10 mg/kg, whereas the D-enantiomer was ineffective at this dosage.(ABSTRACT TRUNCATED AT 250 WORDS)