The DNA-binding protein nuclear factor-κB (NF-κB) is a pleiotropic transcription factor which regulates the transcription of specific target genes such as cytokines. The existence of NF-κB has not been reported in brain tissue. This is the first report demonstrating the expression of NF-κB in the rat brain. After pentylene tetrazole (s.c)-induced clonic-tonic seizures at an LD 50 dose of 85 mg/kg, we have shown a gradual increase in NF-κB expression reaching a maximum at 24 h, a decrease at 48 h and again increased at 96 and 120 h. A similar time-dependent pattern was observed for the NF-κB subunit p50 expression. The NF-κB subunit p65 was not expressed at all. These data suggest a possible underlying mechanism of signal transduction and transcriptional regulation of late-response genes after perturbations in the CNS milieu.