Both direct and indirect environmental stress to brain were increase the expression of transcription factor c-fos in various populations of neurons. In this study, we examined whether the intraperitoneal injections of lidocaine at doses inducing convulsion within 10 min increased the level of c-fos mRNA and protein in forebrain areas. In situ hybridization using [35S]UTP-labeled antisense c-fos, cRNA increased c-fos mRNA levels though hippocampal formation, piriform cortex, septum, caudate-putamen, neostriatum, and amygdala within 2 hr. In parallel with the mRNA expression, c-FOS protein immunoreactivity was also observed in the same forebrain areas. In contrast to the seizure activity and widespread neuronal degeneration following a kainate treatment, injections of lidocaine did not produce neuronal death within 3 days. The present study indicates that lidocaine induces convulsion and c-fos expression without causing neurotoxicity.