The antidepressant drug fluoxetine inhibits persistent sodium currents and seizure-like events

The antidepressant drug fluoxetine (FLX) has been shown to exert antiepileptic effects in several animal models, but mixed preclinical findings and occasional reports of proconvulsant effects have led to hesitation towards its use in epileptic people. Despite being developed as a selective serotonin reuptake inhibitor, FLX has numerous other targets in the brain. One of the proposed targets is the neuronal sodium channel, which is inhibited by many existing antiepileptic drugs. In this study, we used electrophysiological methods in a brain slice model of seizures to test for anticonvulsant and Na(+) channel-blocking effects of FLX. This approach allowed us to use a single biological system to study the effects of FLX on (1) epileptiform activity, (2) Na(+)-dependent action potential generation, and (3) the persistent Na(+) current (I(NaP)). We found that FLX was anticonvulsant in a dose- and time-dependent manner, and that this action was accompanied by strong I(NaP) inhibition and impairment of repetitive firing. These findings suggest that the effect of FLX on active membrane properties is similar to that of many antiepileptic drugs, and that this action may contribute to anticonvulsant effects.