The exact role of compounds modulating nitric oxide (NO) content in the brain during seizure phenomena is under intensive investigation. This study was aimed at determining the effect of NG-nitro-L-arginine (L-NA; a non-selective NO synthase inhibitor) on the anticonvulsant activity of four second-generation antiepileptic drugs (AEDs: gabapentin [GBP], oxcarbazepine [OXC], tiagabine [TGB] and vigabatrin [VGB]) in the mouse pentetrazole (PTZ)-induced seizure model. The acute adverse-effect liability of the studied AEDs in combinations with L-NA were evaluated in the chimney test (motor coordination). Results indicate that L-NA (40 mg/kg; ip) significantly reduced the anticonvulsant activity of OXC in the PTZ test, by increasing its ED50 from 20.9 to 29.8 mg/kg (p < 0.05). Similarly, L-NA at doses of 20 and 40 mg/kg considerably attenuated the antiseizure effects of VGB by raising its ED50 from 595 to 930 mg/kg (p < 0.05), and 1022 mg/kg (p < 0.01), respectively. L-NA at lower doses of 10 and 20 mg/kg did not affect significantly the anticonvulsant effects of VGB and OXC in PTZ-induced seizures. Likewise, the co-administration of L-NA(40 mg/kg; ip) with GBP and TGB was associated with no significant changes in their anticonvulsant activities in PTZ-induced seizures in mice. Moreover, none of the examined combinations of L-NA (40 mg/kg; ip) and second-generation AEDs (at their ED50 values) affected motor coordination in the chimney test. Based on this preclinical study, one can conclude that L-NA reduced the anticonvulsant activities of VGB and OXC in the mouse PTZ-induced seizure model. Only, GBP and TGB were resistant to the action of L-NA in this model.