The effects of vinpocetine and phenytoin on voltage-gated Na+ channels were examined on cultured cerebrocortical neurones of the rat using a conventional whole-cell patch-clamp method. Vinpocetine and phenytoin decreased Na+ currents in a concentration-dependent manner, with IC50 values of 44.2 +/- 14.6 and 50.5 +/- 17.4 microM, respectively. Both compounds shifted the voltage dependence of the steady-state inactivation of the channel in the hyperpolarising direction. This pronounced Na+ channel blocking activity may contribute to the neuroprotective and anticonvulsant effects of vinpocetine.