D,L-homocysteine thiolactone (H), a reactive homocysteine metabolite, contributes to total homocysteine pool. The aim of the present study was to determine the effects of H after acute application in increasing doses to rats. Adult Wistar rat were intraperitoneally administered saline or H in increasing doses (5.5, 8.0, or 11.0 mmol/kg). For electroencephalographic (EEG) recordings, three gold-plated screws were implanted into the skull and animals were supervised. We observed H-induced two types of seizures, the coexistence of convulsive and nonconvulsive epilepsy. Dose-related increase in the number and severity (0-4) of displaying convulsions was recorded. In H(5.5) group, the majority of seizure episodes were grade 1 (62.5 and 0% lethality), in H(8) 40% grade 2, and in H(11) grade 4 in 42.11% (100% lethal outcome). EEGs recordings in convulsive animals showed a high-voltage spike-wave and polyspikes complexes. The second, absence-like, nonconvulsive seizures were accompanied by the EEGs mostly with 6-8 Hz spikes-and-wave discharges (SWD). Latency time to the generalized clonic-tonic seizures overlapped with the time of the maximal median number and median duration of the SWD per 15 min during 90-min observing period. The results show that acute H administration significantly changes neurons, EEG tracings, and behavioral responses and suggests a possible model for studying petit mal epilepsy.